A lease is an agreement between an owner (the lessor) and a user (the lessee) for the use of a physical asset — in trucking, usually a tractor or trailer. The lessee pays to operate the equipment without buying it outright.
Leasing lets a carrier or driver run equipment without the full upfront cost of ownership. A related arrangement, the lease purchase agreement, adds the option to eventually buy the equipment — a path some owner-operators take into truck ownership.