There are three standard types of tracks used worldwide. They are often termed "H", "J", and "L" track, after the names of the manufacturers that established the standards, Halo, Juno, and Lightolier. To identify a track fixture, if it has three contacts, it is likely an "H" type. If the contact-tips are 1 inch apart, it is likely a "J" type, but if they are 7/8 inch apart, the track is likely an "L" type. Many systems now use a single live and then use digital control interfaces such as DALI to control the fittings. This means that each fitting can be independently controlled.
Typical systems have line voltage running through a recessed track. The track may have more than one live conductor, so that multiple switched circuits can be used to control different fittings on the same track. Installers will place the tab of the connector on the fixture to one side or the other when attaching it to the track.
Track lighting is usually combined with directional lamps with reflectors, such as spotlights. These lamps can run under either mains voltage or a lower (often 12V) voltage.
It is common to see line-voltage tracks with low-voltage fixtures. For these, each fixture requires a small built-in Driver to operate it. Alternatively, more modern systems are available with low voltage (10, 12, or 24 volts) running through the track, which is in itself decorative.