Okay, kiddo, have you ever scraped your elbow or knee and it started bleeding? That's called a cut, and the blood comes out of our body through the tiny tubes called blood vessels.
Well, a long, long time ago, people believed that when someone was sick or had a disease, there was too much blood in their body, and they needed to get rid of some of it. So, they came up with a way to take blood out of the body on purpose to try and make people feel better. This process was called bloodletting.
To do bloodletting, people would use sharp tools called lancets to make little cuts in the skin. Then they would let the blood come out into a container or something like that. Some people did it on their own, using things like leeches to suck out the blood. Others would go to a special person called a bloodletter to do it for them.
People thought that bloodletting would help with all kinds of problems, like headaches, fevers, and even mental illnesses. But unfortunately, it didn't really work, and actually made things worse! Taking out too much blood made people weaker and sicker.
Nowadays, we know that blood is really important for our body, and we don't do bloodletting anymore. Instead, we have modern medicine and treatments to help people when they are sick. So, we don't need to worry about taking blood out of our bodies anymore.