What is Nth and how can I describe it?

Hi Guys! tomorrow i am giving a training about Excel dashboard, i just need to know about Nth and K'th, how can i describe/define these things?

It's unknown or not any particular number in a sequence...

For example if you counting people from 1 to 1000 then you go from 1st, 2nd 3rd, etc.... n-th... etc... 1000th.

Why n-th and not 99-th for example?
Because 99-th give you information of a specific number.
And n-th doesn't. It can be any number. Therefore N is more general.

K is same as N.
Sometimes you need both of them if you have two loops.

thank you so much.