What concept can explain the multiresolution modifier

Hello guys!
Within a modeling either with polygonal base or in the sculpture that is the sculpt mode. What concept do you have about the multiresolution modifier in this workflow? What options are in this modifier that can contribute to a modeling?

Thank you

The multiress modifier is exclusively designed for Sculpting, allowing you to have several layers of detail. so you can sculpt, and go to a very very high resolution to add fine details, and then step back to save on performance later down the line, but still maintain those details.

But the options that are in this modifier like:
The delete higher, reshape and apply base.
What utilities have to be applied in the mesh as in a character.
How would it be useful for a worked or sculpted mesh?