Drawer units replace swing doors with full-extension drawers that usually hold GN pans or baskets. When a drawer opens, everything in it is visible from above and can be lifted out directly. This makes them faster to work from on a busy line than a door cabinet, where items at the back are hard to see and reach.
Drawers lose less cold air when opened than a door does, because cold air sinks and stays in an open drawer while it spills out of an open door. The trade-off is mechanical: runners and gaskets carry heavy loads and get daily use, so build quality, runner rating and ease of cleaning are worth checking. Drawers also store less total volume than the same size door cabinet.
A North Indian restaurant in Lucknow might use a two-drawer unit under the tandoor counter for marinated meats in deep GN pans, with the cook pulling a drawer, lifting out skewers and closing it in one motion.