The grate is the metal mesh-like structure found on the base of the rasp. The large gaps in the grate allow it to remove more material from plasterboard than other blades, but mean it does not produce as smooth a finish.
Handle
The handle is used to hold the rasp and can be made of either wood or plastic. Plastic handles will often be shaped (ergonomic) to increase the comfort while using them.
Groove
The groove underneath the grate helps to prevent plasterboard dust from being trapped between the grate and the handle, which would clog up the grate, making it less effective.
