Home point is set by GPS location of the Drone before (and if you can't wait) during take-off. Home Point can also be set to be the position of the RC controller - and that position can be re-assigned through the flight (e.g. you have moved and want to update the home point to your current RC controller position).
You might be referring to a 'way-point' which is a point in a flight plan - which is something a bit different ...
Your Mavic automatically records a home point at the launch point (unless you are impatient and launch before getting GPS).
During your flight you can reset your home point to a new location.
You have the option of resetting it to:
The current location of the drone .. or
The current location of the controller (if you have a GPS enabled phone or tablet)