Idiopathy, kiddo, is a big word that describes a situation when doctors can't find what's causing a person's illness or disease. It's like when you have a problem with your toy, and you don't know what is making it not work. Sometimes, doctors can figure out why you're feeling sick or what is making you unwell, but other times they can't, and it's called idiopathy.
Think of it this way: imagine you have a puzzle, but some of the puzzle pieces are missing. It's hard to complete the puzzle and see the entire picture because some parts are missing. The same goes for some illnesses; sometimes, doctors can't find all the pieces of the puzzle to figure out what's wrong because they're missing important information.
When the doctors can't figure out what's causing a person's illness, they call it idiopathy. It's not their fault or the person's fault that they can't find what's wrong. Sometimes our bodies can be mysterious, and it's tough to figure out what's going on. But don't worry, doctors keep looking and researching so that they can eventually find the missing puzzle pieces and help people feel better.