100W is the tier where a docking station can keep a working laptop charged while it is actually working. Lower rated docks often hold a machine steady when it is idle and lose ground the moment the processor is loaded, which shows up as a battery slowly draining while plugged in.

The figure describes the USB Power Delivery capability of the charging port. Reaching the full rate requires a cable rated to carry it, which is why the supplied cable matters and why a generic USB-C lead often results in slower charging with no error message.

Note that the dock power supply rating and the power reaching your laptop are two different numbers. Everything the dock runs, including attached drives and a monitor drawing power over USB-C, comes out of the same budget first.