A beneficiary is a person who gets something nice, like a present or money, from someone else. It's like when your grandma gives you a gift for your birthday or you win a prize in a contest. The person giving the gift is called the "benefactor" and the person getting the gift is called the "beneficiary".
But when we talk about beneficiaries in more grown-up things like life insurance or retirement plans, it means someone who will get the money or property that belonged to someone who passed away. For example, if your grandpa had a life insurance policy and he named your mom as the beneficiary, it means that if grandpa passed away, the insurance company would give the money to your mom.
Beneficiaries can also be named for other things like bank accounts, property, and even cars. It's important to think carefully about who you want to be your beneficiary because once you name someone, it's hard to change it. Always make sure to talk to a grown-up, like a parent or lawyer, to help you make good decisions about beneficiaries.