Alternate Executor, Generally
An alternate executor is the person or entity you wish to have serve as the personal representative, but only if the primary executor does not serve.

The alternate executor may be appointed when the primary executor is not initially appointed for any reason, as well as when the primary executor is initially appointed and later stops serving.  If the primary executor survives you and fulfills the executor's duties, the alternate executor will not serve in that role in any capacity.  You are not required to name an alternate executor.

See: Executor, Role and Duties; Executor, Eligibility; Executor, Ineligibility