A more thorough explanation:

Remainder

A future interest in a third person who is intended to take after the natural termination of the preceding estate. For example, if a grant is “to A for life, and then to B,” B's future interest is a remainder. If there is only one preceding estate and the remainder vests on that estate's expiration, the remainder is also termed an executed estate.

There are different types of remainders:

• Vested remainder: A remainder that is given to an ascertained person and that is not subject to a condition precedent. For example, “to A for life, and then to B.”
• Contingent remainder: A remainder that is either given to an unascertained person or made subject to a condition precedent. For example, “to A for life, and then, if B has married before A dies, to B.”
• Defeasible remainder: A vested remainder that will be destroyed if a condition subsequent occurs. For example, “to A for life, and then to B, but if B ever sells liquor on the land, then to C.”
• Indefeasible remainder: A vested remainder that is not subject to a condition subsequent. For example, “to A for life, and then to B absolutely.”
• Remainder subject to open: A vested remainder that is given to a class of persons whose numbers may change over time and that is to be shared equally by each member of the class. For example, “to A for life, and then equally to all of B's children.”
• Cross-remainder: A future interest that results when particular estates are given to two or more persons in different parcels of land, or in the same land in undivided shares, and the remainders of all the estates are made to vest in the survivor or survivors.
• Charitable remainder: A remainder, usually from a life estate, that is given to a charity. For example, “to Jane for life, and then to the American Red Cross.”

Remainders can be created by a will or a deed. They are important in estate planning and property law.