I highly recommend that you rewatch the second video in the Variable Frequency Drive Systems unit, because it goes into a lot of detail answering this very question. There’s even a helpful diagram near the beginning of the video.
To briefly answer your question: the motor in a VFD system will always be a BLDC motor run by an inverter board. The inverter runs the BLDC motor by sending 3-phase AC power through it, the voltage of which varies depending on what instructions the inverter has received from the main control board. The inverter receives instructions from the main control in the form of a pulse width modulated signal.
Rewatch that video I mentioned, and then write me back if things still aren’t making sense.