Part 1 : Types of roles in Game development companies

All my childhood I thought that games would come by themselves designed and development,like those forest fruits,vegetables which evolve grow themselves(haha i was pretty dumb I know),but during my teens I realized I was wrong and there's a section  "Credits" entirely dedicated to the crew who contributed for game creation.

Designers

Game designers idealize the game concept,pitches the look-n-feel of game world,designs the scoring and leveling system like Expericence(XP) healthpoints(HP) Damage meters(DMG),sets the rules and constraints, drafts mechanics and hazards, expresses playable characters and enemies concept to artists and programmers to match the gamekind.Simply I would call to Game designers has the heart of game development cycle.

Game designer idea's to reality

• Level Designer - A level designer particularly works on creation of stages,Maps, rounds and levels of game world with the incorporation of objectives,protocols, mechanics and hazards suitable for distinct levels.They compose the look-n-feel of the level world such as where the gameplay occurs like "open-worlds of ice and fire,Space stations,outer space,factory,haunted graveyard themes etc. "
• System Designer - System designers generally work on "Economy" of  games.  Eg: Like the scoring when a player collects certain score objects,Healing-n-damage points when attacked or got beaten up ,costs of weapons, potions,Ammo,Clothing,upgrades etc all the wealth system is designed by them .The true intellect of system designers knowledge exhibit for strategic games like Age of empires series,Civilization series or  city building game types to name few.
• Scripters - The script designers are generally non-identical to scriptwriters.The scripters choreograph the game rules and objectives which occur at run-time of play. Eg: If a player wants to open a locked room he has to search the entire level map for key to open and explore the room space,so the scripter job here is to design a objective in such a way that "if player has key = open Door" or "else = Door  Closed until the key is found".
• Combat designers - Combat designers usually work onto choreograph the moves which  players execute during game-play.They design the punches like jab,uppercut,ground pound (like the Hulk when pounded on ground creates a shock wave to distort enemies position and objects) etc , Lunges to strike the enemy with sword or weapon,free kicks to knockout the opponent,push and grapple ,block and counter attack,flip over, crouch etc like all these moves are designed by them.The true expertise of combat designers showcase for action games like Street fighter series,Mortal kombat series,Tekken series etc. Generally combat designers aren't mandatory because if a game is all about sports genre like EA's cricket or tennis then combat designers aren't required.
• Creative Design director - Creative director is the lead designer among all other designers he's generally the manager or governing head to Design department. He can pitch or ditch the game concept,art,rules,mechanics,hazards etc if unfit to game-play.He guides and regulates his team-design members for better product. Creative director is highly responsible to producers and business officials like(Marketing Dpt.) during every stage of game's pre-production,production and post-production.

Tip : To all the aspiring game designers out there,the most important and fundamental skill required for Game designers is Communication - the ability to transform ideas and concepts effectively to the Artists and Programmers to convert made into minimum viable product.

Writers

Video game writers create main plot of a video game story/theme.They work closely with design Dept. during pre-production stage,they are highly responsible for character creation,world development and activities designed. Game Writers are very similar to Screenwriters in films,they structure the game story into 3 parts.

Game writer

1.Beginning - Prologue or concept of game

2.Middle - Drama or action events

3.End - Finishing of the game story with exciting action sequence like defeating giant bosses in fights.

Writers highest skill exhibit at narration of story and focus on dialogue writing with wit-humor or dramatic melancholy articulation of story if necessary to the plot. Technical writer is the head of writing dept,he/she crafts the video game writing depending to the style of game-play design.Though vast majority of people argue games do not require great compelling story to narrate, but compulsory require great game-play experience and other group of people argue "Games with story elements create great immersion experience to players with mixed feelings of empathy,compassion,rage,enthusiasm etc" and its always a debate topic whether or not to integrate  story elements in games.

Artist

Game artists are craftsman who alter idealized concepts such as character,environment,properties,textures,vehicle assets,3D-2D models,UI/UX,Animations etc creations into art forms.They create the conceptualized art into rough sketches during the pre-production stage and after selection they turn into 3D-2D assets depending to game style .The Game artist also work on to create demo's,trailers,teasers,screenshots which mostly impact to customers because people often judge a game by graphics and the look-n-feel.Depending on the role each artist is much more specialized into many forms.

Game Artist

• Storyboard Artist : Like film story boarding,game storyboard is much alike where the entire game concept is conveyed into graphical illustrations with pictures,sketches in sequence for the purpose of visualization via motion graphics or pictures during the early stages of pre-production.So its the job of storyboard artist to pitch a game concept art into visual representation for all the technical and marketing officials like publishers. 
• 3D modelers : A 3D modeler creates a three-dimensional models like characters,vehicles,Props,costumes etc.They generally use industrial standard multimedia software tools like 3DS max,Maya,blender etc to create them.The modelers require diverse set of skills with both artistic skills and technical abilities.They are directly responsible to Lead Artist in every game development life cycle.
• Environmental artist : They transform their artistic skills into art forms with main source targeted to Nature .They work to create mountains,terrains,landscapes,lava's,oceans,farm fields etc in 3D computer graphic softwares which mentioned above.
• Texture artist : Texture artist create the visual textures for game characters,world and objects.Textures are widely ranged from tiles,wood,roads,trees,sand,mud to sci-fi textures such as plasma,electric wall texture,laser point textures etc.
• UI artist : UI artist generally design/create the HUD elements like score,Life chances,recticule-aiming system,damage meter to fonts etc. UI/UX artist generally work onto create graphical interfaces which look great and player-friendly.They strive to eliminate low-grade designs to maintain industry standard UI asset creations.
• VFX artist : visual effects/VFX artist create artificial effects in computer generated software's.They create visuals such as fire,ice,water,distraction of buildings,collapsing of lavas into oceans etc.There main talent showcases during the creation and designing of game trailers and live action teasers.
• Art director : Art director are artistic Head of Art Dept.He's solely responsible to designers and publishers. Art Dir's guides and maintains the workflow with peer team artists.He also has the ultimate power to pitch or ditch the Art concept if it doesn't fit into game bounds.

Audio engineers

Audio engineers or composers are responsible to create sound effects in games,they add audio elements like heavy breath,cry,thump,thud,clap,boom,smack etc sound effects to turn immerse the player much more into virtual worlds.There true skill showcases for survival horror games where sound effects are crucial for mood generation and involvement into game scene.

Music notes

• Music composers : They compose the Music or soundtracks to games which will be cued during the gameplay sessions. The music must generate the feel-n-mood of accomplishment,empathy,fear etc to players in game scene and it must match with the certain game theme. 

Composer

Bonus Tip : Video games provide the ability to improve focus,mortar skills and also trains to bestow solid foundations in logical and reasoning abilities thru puzzles.