Texture Coordinates

Texture coordinates, also called UVs, are pairs of numbers stored in the vertices of a mesh, and often used to stretch a 2D texture onto a 3D mesh.

UV Tutorials

How to plan good UVs is in the UV Theory thread on Polycount.
Good methods for UVing spheres can be found in the Unwrapping a sphere thread on Polycount. For sphere modeling tips see Sphere Topology.
A good weapon UV can be found in the tutorial First-Person Weapon UVs by Joe 'EarthQuake' Wilson
A good character UV example can be found in the tutorial Maya / Mudbox: Street Cop Workflow by Mashru Mishu.
How to prevent 3ds Max subdivision from distorting UVs is in the uv + turbosmooth= big problem thread on Polycount. A similar thread: Best way to approach unwrapping UVWs with Meshsmooth?
For an automated UV projection system, see 3D UV projection network in Maya by Paul 'prolow' Lohman
See also Light Map Texture Coordinates