What is UV mapping?

Picture peeling an orange and pressing the peel flat. That's what UV unwrapping does to a mesh. The flattened pieces are called UV islands, and the cuts between them are seams. "U" and "V" are simply the horizontal and vertical axes of the texture image, named so they aren't confused with X, Y and Z.

What makes good UVs

• Little stretching. A checker texture should show even squares across the model.
• Hidden seams. Place cuts where they're unlikely to be seen, such as under arms or along hard edges.
• Consistent texel density. Similar-sized parts should get similar texture resolution.
• No accidental overlaps, unless you deliberately mirror symmetrical parts to save space.

UVs and generated models

AI-generated meshes come with automatic UVs that work but are often fragmented. That's fine for viewing. It becomes a problem when you want to repaint the texture by hand, and the usual fix is to re-unwrap in Blender, then bake the old texture onto the new layout.