Combination vs. permutation + calculation (23 and 23)

Question

I have 23 options for category (number) and 23 options for category (letter). For example: 1a, 1b, 2a, 2b; (1a is not the same as 1b or 2a). Is this a combination or a permutation? How do I calculate this and how do I know which one it is?

Answer 1

Permutation: the order makes a difference, e.g., ab is different from ba.

Combination: the order does not make a difference, e.g., ab is the same as ba.

What you have is the "counting principle."

23 objects paied with 23 other objects

With 1 you can pair 23 letters

With 2 you can pair 23 letters

With 3 you can pair 23 letters

And so and so on an so on

So you have (23)(23) difference pairs.