Characterized by a right of survivorship.
On the death of a joint tenant, his or her interest(e.g.house) passes automatically to the survivor. The joint tenant cannot pass his or her interest by will to another person. The transfer of title through surviving joint tenancy saves taxes, and may have other estate planning benefits.
If a joint tenant separately mortgages or sells his or her interest, this "severs" the joint tenancy, and it automatically becomes a tenancy-in-common.
Joint tenancy is the usual option for spouses, but can be used in other situations.
Consult your lawyer