In order to understand the importance of anti-lapse, you must know what it means to say that a testamentary gift has lapsed. When such a gift lapses, it means that ownership of the gift has failed to transfer because the gift’s beneficiary dies before the testator. Anti-lapse statutes prevent a testamentary gift from failing; in other words, when the person who was supposed to receive the gift (i.e., the beneficiary) dies before the person who wrote the will (i.e., the testator), these statutes keep the gift from lapsing.
What happens when a beneficiary predeceases the testator will depend on the type gift being made in the will. If the gift is being made from the residual estate, the jurisdiction’s intestacy statutes will determine what is to become of it. The residuary estate is that portion of the decedent’s estate that was not specifically named elsewhere within the will. Intestacy is the name for those situations where someone dies intestate (i.e., without a valid will). For example, Bob’s will states that his residual estate is to go to Charlie, Diane, and Ed, in equal shares; if Charlie dies before Bob, his one-third share of the residual estate will pass via the intestacy laws in that jurisdiction. Where it is a specific, demonstrative, or general gift that is being made, the usual course is for the gift to become part of the residual estate, unless the will states otherwise.
To find out how anti-lapse is applied in your jurisdiction, speak with an estate planning attorney.