Pigeon hole principle doubt

Question

Question

Of 12 distinct two digits numbers we can select 2 with a two digit difference of the form aa

Can anyone please explain me what this question means

Answer 1

The statement says that in any set of twelve distinct two digit numbers (i.e. twelve numbers between $10$ and $99$ where no two are the same) then there are two numbers whose difference (absolute value of one minus the other) is a multiple of $11$.

Presumably the associated question is asking you to prove this.

To apply the pigeon hole principle, put the twelve numbers into pigeon holes that represent the remainder when each number is divided by 11. What can you conclude about the difference of two numbers if they re in the same pigeon hole ?