Yes I know some of it is self-evident but please be helpful and as detailed as possible. I'm still learning. Thank you. 01. Sound Designer 02. Composer 03. Texture Artist 04. Pixel Artist 05. 2D Artist 06. 3D Artist 07. 3D Animator 08. Concept Artist 09. Programmer 10. Engine Programmer 11. Game Programmer 12. Game Designer Do any of these jobs overlay?

I could or I could let you GOOGLE it!

1 = Makes sound effects
2 = Makes music
3 = Draws 2D pictures of surfaces (e.g. bricks) that will be used by person #6. Often this can be the same job (e.g. 3D modelling and texturing of the model).
4 = Much like 3, but probably more towards Icons, HUD elements etc. Or, on 2D games, characters/environments are made with sprites, not models, so a artist that is good at drawing these things in 2D might be called a "pixel artist", especially if working in low-resolutions (e.g. Nintendo).
5 = See 3/4
6 = Models things in 3D (e.g. using 3DSMax). This could be characters, props (items/objects in the game) or environments (the actual levels).
7 = Rigs up models and makes the animation sets for them. Rigging and animation can be two separate jobs, or these could even be the same job as #6.
8 = 2D artist that draws pretty pictures to guide/inspire all the other artists (and programmers)
9 = see 10/11
10 = Builds the libraries that are reused on more than one game
11 = Builds things specific to a single game
12 = Varies a lot from company to company. Could be anything from story writing, spreadsheet tweaking, level planning or even puzzle ideas.

As for overlap, it really depends on how many people are on your team and what their skillsets are. You could have just one programmer, who at any given time may be working on the engine, the game rules, the resource management, etc. Your concept artists might well also take their concepts and turn them into models or 2D sprites. Hell, I'm doing everything on your list myself for my project, except for composer, since composition is a skill I've not gotten around to picking up.

Blizzard would have little to no overlap between those jobs, because they can employ so many people that it makes sense for their employees to specialize. A place like Three Rings Design can't afford to have that level of specialization, though, so their employees wear multiple hats.