There are many different parties in a Last Will & Testament, and each has a different role.
Testator/Testatrix: A Testator or Testatrix is the person that the Will is being created for and whose property will be distributed once they are deceased.
Executor/Personal Representative: An Executor is the person who the Testator or Testatrix has designated to administer their wishes in terms of how the estate will be divided. You may have more than one executor, and you should have an alternate personal representative should anything keep your first choice from being able to carry out your estate plans.
Beneficiary: A beneficiary is someone who will receive either an aspect of, or all of your estate. You may name multiple beneficiaries and divide your assets as you see fit.
Pet Caretaker: If you have pets, a pet caretaker is someone who you would name to care for your pet upon your expiration.
When considering who should be your executor or pet caretaker, ensure that it is someone trustworthy and someone who can handle the weight of managing your affairs after you pass away. Talk to your executor and pet caretaker beforehand to ensure that they are willing to be a part of your Last Will & Testament.