Analog/Digital ground vs Power/Signal ground
Some power ICs require separate power and signal grounds.  This is so the IR drops and switching noise don't impact the current or voltage sense or compensation pin for example.  Generally the power and signal grounds connect at one point often near the power ground of the IC.  This all happens locally on the board and is independent of any digital and analog grounds elsewhere.  If you have discrete power circuitry on the board the same guidelines can help.

Analog vs. digital ground is also usually specified on some ICs, and is also a good idea because it keeps the digital switching noise out of the sensitive analog circuitry which is usually trying to measure something accurately.

So carving up the ground plane locally for all the different purposes is OK and desirable, though sometimes based on experience you can get away with combining "noisy" grounds and "quiet" grounds into single planes.