Okay kiddo, so imagine you're trying to understand what someone is saying but they're speaking a different language. You don't know any words in their language and they don't know any words in your language. But you really want to understand what they mean, so what do you do?
Well, one way is that you could guess what they mean based on their actions and gestures. So, if they're pointing at a picture of a cat and making purring sounds, you might guess that they mean "cat" or "kitty". This is sort of like playing a guessing game, where you try to figure out what someone is saying based on clues you see around you.
Radical interpretation is kind of like that guessing game, but with language. Philosophers use the term "radical" to mean getting to the root or core of something. So, radical interpretation is when you try to figure out the core meaning of what someone is saying, even if you don't know the words they're using or the cultural context they come from.
So, imagine you meet someone from a far-off land who doesn't speak your language. You want to know what they're thinking and feeling, but you don't know what any of the words they're saying mean. You could try to guess based on clues like their facial expressions, tone of voice, body language, and so on.
But that's not always reliable, because people can express emotions in different ways and cultural differences can change the meaning of gestures. So, radical interpretation tries to look beyond those surface-level clues and get at what someone means at a deeper level.
One way to do this is to assume that there's a shared set of beliefs or ideas that all people have in common, no matter what language they speak or culture they come from. These might include things like basic logic (e.g. if A is true, then not-A can't also be true), causality (e.g. if I drop a ball, it will fall to the ground), and intentionality (e.g. people do things for reasons). By using these shared ideas as a starting point, you can try to figure out what someone means even if they're not using words you know or understand.
Of course, this process can be really tricky and there's always room for error. But philosophers use radical interpretation to try to understand how humans communicate and make sense of the world around them, even when they come from very different backgrounds.