Okay, so Americanist Phonetic Notation is a special way of writing down how words are pronounced. It's really helpful because sometimes words can sound different depending on who is saying them or where they are from.
Think of it like a secret code that only people who know how to read it can understand. Instead of using regular letters like A, B, and C, Americanist Phonetic Notation uses special symbols to show exactly how a word sounds when it's spoken.
For example, instead of writing the word "cat" normally, in Americanist Phonetic Notation it would look like this: /kæt/. The symbol /k/ shows the sound at the beginning of the word, and the symbol /æ/ shows the sound in the middle.
It might look a little confusing at first, but once you learn how to read it, it can be really helpful for understanding different accents and dialects.