What is a solder wick?

Desoldering braid or “wick” is a pre-fluxed copper braid that is used to remove solder, which allows components to be replaced and excess solder (e.g. bridging) to be removed. The soldering iron is applied to the wick as it sits on the solder joint, and when both are brought up to the solder's melting point, the flux is activated and, through capillary action from the braided design, solder is drawn up the wick.