In musical terms, “comping” is instrumentally accompanying a vocalist or soloist.
In concert promotion terms, “comping” is giving someone free tickets to a show.
But you’re probably asking about “track comping,” which is the process of editing audio recordings of multiple performances into a single performance, to create a “composite” audio recording, called a “composite track” or a “comp” for short.
Most modern DAWs have track comping features. Comping is extremely useful when you want to create a single, clean “best of” performance out of numerous performances that each had mistakes or weak phrases or notes at different points. Comping can also be used creatively to assemble a performance from parts. For example, you might record 10 different versions of a guitar solo, then edit your favorite parts of all 10 together to create one new “comped” guitar solo.