A WIP is a work in progress — a crochet or knitting project you've started but not yet finished. Makers often keep several WIPs going at once, and a long-neglected one is affectionately called a UFO (unfinished object).
Tracking WIPs — which project, which yarn, where you left off — is part of the craft. Many makers keep project notes so they can pick a piece back up months later without losing their place.