Night sweats are when your body gets very hot and sweaty while you're sleeping. It's like your body is having a big heat wave at night time. It can make you feel really uncomfortable and make it hard to sleep.
There can be lots of different reasons that someone might have night sweats. Sometimes it happens when you're sick, like if you have a fever or a cold. Sometimes it happens if you're taking certain medicines or if you've been drinking alcohol. Sometimes it happens if you're going through puberty or menopause, which are times when your body is going through big changes.
If you're having night sweats a lot, it's important to talk to a grown-up you trust, like your parent or your doctor. They can help figure out what might be causing the night sweats and what you can do to make it better.