Okay kiddo, have you ever heard of the word "peri"? It's a shortened version of the word "perimeter", which means the outside edge of something.
Let's say you have a toy block. The perimeter of the block would be the distance around all four sides of the block. Imagine taking a string and wrapping it around the block to measure the length of the perimeter.
Now, the word "peri" is often used in certain medical terms. For example, if a doctor says you have peri-tonsillar abscess, it means you have an infection that's located around your tonsils. "Peri" can also be used in other medical words to describe situations where something is located around a certain body part.
So, long story short, "peri" usually means something is located around the outside edge of something else!