Adaptive representation means changing the way you explain something depending on who you're talking to.
Think about when you try to teach your little sister something, like how to tie her shoes. You use simple words and break it down into small steps, because you know she doesn't understand complicated ideas yet. That's adapting your representation!
The same can be true with more complicated ideas, like explaining math problems or scientific theories. Sometimes you need to slow down or use pictures to help someone understand, and sometimes you can use big words and complex ideas if you're talking to someone who already knows a lot about that topic.
Adapting your representation is a way of being considerate to the person you're talking to, because it helps them learn and understand. It's like speaking their language!