What is a UV map?
Exactly why is a UV map anyways?
If you have used many sculpts, you are no doubt familiar with a texture map. This is basically a flat 2D texture that when applied to the sculpt, would help you identify the different parts of the sculpt. Using the texture map, you could put different details on different parts of the sculpt depending on exactly what you are looking for as a final result.
A UV map is basically the same thing, but for meshes. They are designed to make it much easier to texture a mesh and allow you to work with a lot more detail in some cases.
More detailed info can be found by looking here if you like also.