Overparenting is when a grown-up takes care of someone - like a child, even if they're not small anymore - too much. Imagine being a little kid and a grown-up is tying your shoelaces, holding your hand when you cross the road, and cutting up your food at dinner, even though all the other kids who are your age do it themselves.
Now imagine that you're bigger, but the grown-up keeps doing these things for you. That can make the young person feel like they're not capable of doing things on their own, it can make them feel embarrassed or uncomfortable, and they might not learn important skills because someone else is always doing things for them.
So, if a grown-up does too much for a person, that means they're overparenting. It's important for young people to be able to try things and make mistakes on their own so they can learn and grow.