Tearing happens when something that is stretchy, like paper or fabric, gets pulled too hard and it breaks apart. Just like when you pull on a piece of bread that's really soft and it starts to rip.
Things can tear because they're old and worn out, or because they're not strong enough to handle the force being applied to them. For example, if you poke a hole in a balloon with a sharp object, it will tear because the rubber isn't strong enough to resist the poke.
When it comes to our own bodies, we can sometimes tear our skin or muscles if we push ourselves too hard or if we're in an accident. Our bodies are made up of lots of little fibers called "tissue" that hold everything together. When those fibers get stretched or pulled too hard, they can break and cause a tear.
Tearing can be painful, so it's important to be careful with things that can tear easily and to listen to your body if you feel like you're pushing yourself too hard. And if you do happen to get a tear, you can help it heal by taking some rest and letting your body repair itself over time.