Leasing is a process by which a firm can obtain the use of a certain fixed assets for which it must pay a series of contractual, periodic, tax deductible payments. The lessee is the receiver of the services of the asst under the lease contract and the lessor is the owner of the assets. The relationship between the tenant and the landlord is called a tenancy, and can be for a fixed or an indefinite period of time (called the term of the lease). The consideration for the lease is called rent.

Under normal circumstances, an owner of property is at liberty to do what they want with their property, including destroy it or hand over possession of the property to a tenant. However, if the owner has surrendered possession to another (ie the tenant) then any interference with the quiet enjoyment of the property by the tenant in lawful possession is unlawful.

Similar principles apply to real property as well as to personal property, though the terminology would be different. Similar principles apply to sub-leasing, that is the leasing by a tenant in possession to a sub-tenant. The right to sub-lease can be expressly prohibited by the main lease.