ELI5: Explain Like I'm 5

Local field

When you go out to a big field and play around, that's like a regular field. But sometimes, there are smaller fields that are closer to where you live, like in your neighborhood or nearby park. Those smaller fields are called "local fields."

But in math, a local field isn't a place to play, it's a special kind of number system. Just like how you can count with regular numbers like 1, 2, 3, there are also special numbers called "p-adic numbers" that live in local fields.

Now, the way we count with regular numbers is pretty straightforward. But counting with p-adic numbers is a little different. Instead of just counting right or left from 0, you can also count up or down from it. And the way you do this depends on a special number called "p," which is usually a prime number like 2 or 3.

Think of it like playing a game where you can only move a certain distance each time, and that distance depends on your starting point. It's kind of like playing a board game where you can only move 1 or 2 spaces each turn, but you can also "wrap around" the board and move backwards or forwards as much as you want.

Local fields are really important in a lot of advanced math topics, like algebraic geometry and number theory. But for now, just remember that they're like special number systems that use p-adic numbers and depend on a special prime number called "p."