Diameter and thread count refer to the size of screw or bolt the threaded insert is used with. For example, a 1/4"-20 threaded insert fits a 1/4"-20 bolt.
10-32 is a fine thread, but it is listed under coarse thread because it is very common.
Drill bits are cutting tools used to remove material to create holes.
A type of nut used to create internal machine threads in wood or similar materials.