If you are reading someones posts, using the SHOW POSTS function.
And they have a lot of posts, you may want to go to a certain page of the listing.
So in the bottom right corner it say pages 1-xxx
Then there is a black downward facing arrow.
If you click on that arrow then you can enter a page number.

Took me about 2 years to figure that out.

Also the forum defaults can be changed to put more or less posts on a page.

Or you can change what is displayed to look at older posts.

There is a lot of information here but it takes some work to find it all.

Me-68, D35,S34