From LightWiki

A Vertex Map (Or VMap for short)is a way of storing a value or group of values in each vertex of your object. The standard vertex maps in LightWave are:

Selection Sets - A way of grouping points together for selection.
Weight Maps - A single value is stored per vertex. This can be used for Bone weights, which usually go between 0%-100%, but the values can be limitless. they can also be used for controlling point sharpness in Subpatch meshes.
UV maps - Used for special texture mapping of meshes, this is a two-value-per-vertex map.
EndoMorphs - This is used for performing Morphs in LightWave. It is a 3-value map, which stores either the offset of a point from its original position (a Relative endomorph) or the absolute position of the point (surprisingly called Absolute endomorph).
Vertex Colour Maps - Vertex colour maps are typically used in the games industry for colouring meshes, but they can be used elsewhere. Vertex Colour maps come in two flavours in LW, with and without Alpha. Without Alphas are usually referred to as an RGB map, whilst with Alpha maps are called RGBA maps.

Plugin writers can create their own special types of VMaps should they wish to do so.