Subletting is renting an apartment or house to another tenant while maintaining the original agreement or lease with the landlord.
If you sublet your apartment, you are still responsible for the rental agreement or lease. If your subletter causes damage to the rental unit, you are responsible for the repair.
A sublet agreement between you and the person subletting from you is a good idea.
If you signed a lease and would like to leave with no plan of returning, you can request to have your rental agreement assigned to a new tenant. Your landlord must be reasonable in considering whether to approve your request.