Some values shouldn't change after being set. Python doesn't have true constants, but by convention, we use ALL_CAPS names to signal "don't modify this": python MAX_USERS = 100 PI = 3.14159 DATABASE_URL = "localhost:5432" This is just a convention.
Python won't stop you from changing MAX_USERS. But other programmers (and your future self) will know these values are meant to stay fixed. Put constants at the top of your file where they're easy to find and modify if needed.