UV mapping assigns two-dimensional coordinates to mesh vertices so images can be sampled across the surface.

Coordinates
U and V
Connects
Mesh surface to 2D texture
Key concerns
Seams, distortion, density
After retopology
Usually rebuilt

Good layouts reflect how the asset will be seen

Give important visible regions enough texel density, hide seams where practical, and leave padding so filtering and mipmaps do not bleed between islands.

Check more than the color texture

After UV changes, transfer every required channel and verify tangent-space normals in the target renderer. A correct base color alone is not a complete PBR transfer.