Question: What is the difference between a lease and a tenancy?
Answer: There isn't one. They both mean the same. Equally the terms landlord and lessor are the same, and tenant and lessee are the same too.
In practical use, which terms are used tends to depend on the length of the arrangement. If its for week to week or month to month it tends to be called a tenancy. If its for a period of years it tends to be called a lease. Also for business premises there is a slight tendency to use the term lease more often than for residential premises.