A curtain heading is the gathering or pleating at the top of the curtain. This is achieved by sewing a heading tape to the top of the fabric.
The tape has cords that are threaded along the tape and when pulled, they draw up the fabric to its specific style. It has pockets, which receive the hooks to attach it to the track.
Depending on the type of tape there are options for positioning the curtain top above below or equal to the track via the placement of hooks into the pockets. The design of the heading tape will determine the style of the pleating/gathering and dictates the fullness of the curtain.
Gathering tapes requires 1 ½ -2 times the track width, pencil or box pleats require 2 ½ times the track width to create the correct effect.