A contract whereby a tenant pays a landlord, or leaseholder pays a freeholder, for the right to use a property. Leases can be of short or very long duration. Leases are complex documents and specialist legal advice should be sought if you are considering entering into a lease. A lease typically requires rent to be paid (otherwise the contract is usually referred to as a Licence), although this does not have to be a commercial rent, with a peppercorn rent often sufficing.
As a rule of thumb, most houses are freehold and most flats leasehold. If you own a leasehold flat, you effectively rent it for a period of time, specified on the lease.