What does it mean that there are holes in the middle of the independent foundation?

This is the plate hole.

General foundation beam pouring backfill.

Independent foundation is an independent foundation used for single column or high-rise structure. Its type is selected according to the material properties and stress state. The plane form is usually circular or polygonal. However, in addition to dead weight and vertical live load, wind load is the main design load of high-rise structures. In order to make the foundation have approximately the same overturning stability coefficient in all directions, circular foundation is the most suitable.