In case you want a little more info: the purge valve connects the throttle body to the charcoal canister. It’s in a black plastic run of piping that travels from the throttle body along the drivers side of the engine and down the backside of the engine, then all the way back under the car to the canister. Looks similar to the crankcase vent line, but smaller diameter. The valve is supposed to be closed when the car is idling (high vacuum in throttle body), and opens when the car is at higher RPMs and there is some pressure in the tank to pull fumes from the tank through the canister and into the engine. Once failure sign I’ve seen reported is a clicking from the purge valve while the car is idling, though that’s probably not the only mode of failure.
The DMTL pump pressurizes the whole evap system under certain manufacterer specified conditions (car driven x miles with so many drive cycles, then turned off for y minutes, etc.). It pulls in fresh air through a normally-closed fresh air vent. Purge valve should be closed. Once the system is pressurized, the pressure sensors check for loss of pressure over a period of time, which would indicate a leak. If there is a leak, the ECM sets a code.