A will (or last will and testament) is a signed, legally binding document that explains exactly how you want your property and other stuff to be handled after your death.
You can also put information in there about how specific items are to be dealt with, and even appoint guardians for your children if you need to.
Making a will means you can decide beforehand where you’d like your things to go after you’re gone. That’s what a last will and testament is all about: your wishes in who handles your estate or gets all your stuff. Whether you are single or married, it matters.