AC Adapters are power supplies, in that they take AC power and convert it into a supply of DC power that your device can use, via transformers or by other means (such as switch-mode power supplies). This is the same concept any other power supply you have uses, but sometimes things require different power levels or even types. Schitt's headphone amps, for instance, all run off of AC power instead of DC.
Modern devices will only pull as much as they need, because safety circuitry is built into almost all modern electronics. Likewise, a power supply is actually always pulling a small amount of current at all times as long as it is plugged it, but will ramp up the amount it converts with greater demand, up to its physical thresholds.
You don't have to worry about this damaging any of your devices, if that's your concern. ;)
EDIT: This is all dependent on the fact that you have a stable mainline power system that you are plugged into. If your power coming in from outside is unstable, either due to faulty wiring within the building or because of an unreliable provider, then those factors could potentially damage your power supply, your equipment, or both. Though many electronics nowadays will have safety measures against small changes in your main power lines.
EDIT2: OR you overload the building fuses for a local socket because you have too much plugged into it. A regular socket will be able to handle 80W no problem though, as long as you don't have several other high wattage devices (microwaves, air conditioners, high end computers, etc.) all pulling power at the same time from the same outlet/fuse source.
EDIT3: OR if you were actually asking "Will I overload this unit if I plug too much into it" No, you won't. It is designed to handle up to 80W and will not provide more than that even if you somehow manage to saturate its power output, which I sincerely doubt you could unless you plugged in multiple laptops or something.