Split custody is when two parents have more than one child, and each parent has custody of one or more of those children. It's like if you and your sibling have two toys, and your mom says you can have one toy to keep at your dad's house, and your sibling can keep the other toy at your mom's house.
This means that sometimes you will live with your mom and visit your dad, while your sibling lives with your dad and visits your mom. So, you will have two homes and two sets of rules to follow.
Split custody usually happens after a divorce or separation, and it's done to make sure that each child has a close relationship with both parents. It's important for parents to work together and communicate well to make split custody work for everyone involved.