The person responsible for endowing the tenancy to the life tenant is usually the owner of the real estate, the ownership of which is governed by a fee simple absolute.
A good question. Essentially, a life tenant is a person who has the right to some real estate for his or her lifetime. They would usually have relatively unrestricted rights to do what they wish with the real estate while alive, subject to any restrictions in the tenancy or lease agreement, and the relevant law. When the life tenant dies, it also signals the end of the tenancy. The remainderman is the person who receives the real estate when the life tenant dies.