Okay kiddo, have you ever heard the phrase "caught red-handed"? Well, "in flagrante delicto" is kind of like that, but it's a fancier phrase that some smart grown-ups use.
Basically, "in flagrante delicto" means that someone has been caught doing something wrong or illegal right in the middle of doing it. It's kind of like walking into a room and seeing someone steal cookies from the cookie jar - they're in the act of doing something wrong and you catch them right then and there.
So, when someone is caught "in flagrante delicto," it's usually pretty easy to prove that they did something wrong because you literally saw them doing it! It's an important term for lawyers and police because it can help them prove that someone did something bad - and they can't really deny it!