You know how to use character sets.
For example, [abc] will match any character a, b or c.
But what if you need to match a larger range of characters?
For example, from 0 to 9.
You don’t want to write [0123456789] every time, right?
That’s why you can use character ranges.
Instead of typing every character, you can specify from 0-9.
Just like this: [0-9]
Match any character from A to Z (uppercase)