Heirs are recipients of an inheritance from a deceased owner, whereas assigns are successors in interest to a property.
The words heirs and assigns are customarily inserted in deeds and wills, and are considered to be words of limitation, not words of purchase.
Words of limitation in a conveyance indicate what type of estate is created. Words of purchase indicate who takes the estate. For example, in a conveyance “to Harry Howe and his heirs,” the words to Harry Howe are words of purchase.
The words and his heirs are words of limitation indicating a fee simple estate; they would not be present in the transfer of a life estate.
Heirs and assigns are also generally responsible for the contracts of their predecessors, such as leases, options, mortgages, and contracts for deed.