A simple will is a will that gives everything to your spouse and if your spouse has predeceased you, to each of your children in equal shares. For a married couple, each spouse will have a simple will. For a single person, they will have a simple will which gives everything to their children in equal shares or to some other person(s) they name.
DISCLAIMER: Simple wills provide very basic planning.
They may or may not be a good fit for your circumstances.