Ligandfit novice questions

1-why do the ligandfit undergo
Rigid body energy minimization of the candidate ligand pose/conformation using ?

2-Is it necessary to delete water molecules for this module ? I used to perform docking of ligands that can make H-bond bridge with water

3-Is it necessary to apply forcefield to protein before carrying out docking or it is done by default...I want to check the preparation steps required