The right of survivorship is a feature of certain co-ownership arrangements: when one owner dies, their share passes automatically to the surviving owner or owners. Not through the will. Not through probate. By operation of law, at the moment of death.
Three things follow from that definition, and each one surprises somebody every week.
First, it beats the will. If the deed says joint tenants with right of survivorship, the house goes to the surviving co-owner even if the will leaves "my half of the house" to someone else. The will controls what passes through the estate; survivorship property never enters the estate.
Second, it skips probate entirely. The survivor typically records a death certificate (some states add a short affidavit) and the title is theirs. Weeks, not months.
Third, it only exists if the deed says so. "Joint tenants with right of survivorship," "JTWROS," or your state's magic words. Co-owning a house does not create survivorship by itself; without those words, most states presume tenancy in common, which is the probate route described below.