How do you rip Models

[Garamonde]

OK, well, just entirely out of curiosity, how do you put textures that people have ripped onto models? They kinda just look like flat graphics. Can you select them and put them in your model program or something? I always wondered how that worked (though that's probably mostly used for custom models huh).

Also, I edited my last post too late, sorry:

And um, this is probably a silly question but what does "rigging" mean for models? Like being able to position it however you want?

I'm so full of questions.