Overdiagnosis happens when a doctor finds or tests something that is really small, not harmful or not causing any problems, but tells you there is something wrong and gives you medicine or treatment that you don't really need.
For example, imagine that you go to the doctor because your ear hurts a little bit. The doctor does an exam and finds a very small infection in your ear that will go away on its own in a few days, but the doctor tries to give you medicine anyway.
Overdiagnosis is like when you tell your mom that you need a band-aid for a tiny scratch, but your mom says you need to go to the hospital for surgery. It's too much and unnecessary.
Even though it might seem like overdiagnosis is helpful since you're getting more attention and medical care, sometimes it can actually cause harm. Taking unnecessary medicine can have side effects, and unnecessary treatment can be expensive or even dangerous.
That's why it's important for doctors to carefully consider all the information they have about you, like your medical history and symptoms, before suggesting medication or treatment. They need to make sure that any tests or procedures they're doing are really necessary and will actually help you get better.