While texturing a flat object is fairly straightforward, texturing an object with curves can pose some unique problems. How do you paint a 2D texture on a curved surface? How do you deal with a texture warping over bumps and grooves? If you try to break apart the UV mesh like Lesson 1, you can potentially end up with hundreds of small pieces.
To deal with these problems, artists typically use a workflow called unfolding. Unfolding a UV mesh refers to the process of cutting a seam in the UV mesh (a mesh made up of UVs similar to how a polygon mesh is made of vertices) and then unfolding along that seam. The process is similar to cutting a seam along a shirt and laying it flat on a table. By laying out the UVs this way, you can easily paint a texture on the 2D surface, which you can then wrap around the model.