The parties to a lease contract are the lessor and the lessee, or, alternatively, landlord and tenant. Is there a difference between them?
In most situations, they can be used interchangeably. However, definitionally there is a difference between them. Lessor and lessee is the descciption of the parties to a lease of any property, real or personal, while landlord and tenant are used to decribe the parties to a lease when the subject of the lease is real property. The term "landlord" and "tenant" are not used for leases other than real property lease.
There is another apsect of the differentiation. Landlord and tenant are old fashioned terms, their meanings are rooted in traditional common law, where the term "tenant" is imbued with meanning reaching beyond the modern meaning, which is commonly used as a synonym to lessee. Tenant, in the common law, in a specific context, can be an owner of a property.
Therefore, it is safer to use the term "lessee" as a counterparty of "lessor" in lease contracts.