Gathers can be made very simply on any fabric and are generally used to attach a longer piece of fabric to a shorter one. The technique is easier to create on lighter fabrics.
Gathering is one method used to reduce fullness in a garment e.g. gathering around the waist to add shaping, or on a sleeve at the cuff.
Gathers can add decoration or function as desired.
Click the links below for videos on how to gather fabric in different ways:
Gathering (Julia’s sample)
3 ways to Gather – explained by Threads