For most of us that are doing implementation engineering, a lab is simply a collection of the gear that can be put together in a simulation of the production environment without being constrained by formalities. For me it would be a bunch of network and server kit and cables in a rack.
Not OP, but at several jobs our labs were small server rooms stuffed with network gear, servers, and client PCs. They were used for end-to-end simulations and tests. It wasn't uncommon to actually do work in the lab, keeping an eye on the blinky lights or somesuch.