Textures are 2D images that are designed to influence a 3D model's appearance. Whether it's simply to add color to a model like one would paint a clay sculpture, or to govern a specific material attribute, textures can be generated and painted by hand with Blender's built-in tools. The texture process begins with addressing a model's UV coordinates. UVs are the mechanism by which a 2D image is transposed on to a 3D model. It's an art form in itself to layout these coordinates to maximize texel density (amount of texture pixels utilized) while minimizing stretching (disproportion between the model and its UV's). After UV's are established, textures can be painted by hand using a Wacom pen and tablet. Textures can also be generated by "baking" geometric data into image texture format. Alternatively textures can be painted with an external application and easily brought back into Blender. CC Music: "Home Tonight" by DoKashiteru
Its getting old , and there is a better tutorial online on CGCookies
https://cgcookie.com/courses/fundamentals-of-texturing-in-blender?playlist=bjw3r5
This is a very nice course to get into something that I feel is kinda really hard, but also not so hard if you get it right. Try watching it one or two extra times so you really get used to the vocabulary and the interface, what to do where,etc :)