Track is a surface mounted channel that holds the lighting units (or 'heads') in place and brings power to them. Because it is surface mounted, track is particularly easy to install, especially in remodels. The track is usually mounted to the ceiling but it can be mounted to a wall, a beam or dropped from the ceiling on stems or cables.
All you need for a track system is the track, your choice of power connector, and as many track heads as you can fit!
A closeup segment of track

The very necessary Power Feed

A 'floating' power feed