Web-page with the same URL, but different parameters still counted the same to a previous?

For static sites we can have a "page.html". This page do not have any parameters such as "?param=value.

And it will be indexed by search engines and other things. No problems here.

But I would like to know what actually happens with indexation when a single page, for instance "lessons.php?lessonID=1" has some parameters and its content is really different in contrast with page "lessons.php?lessonID=2".

Are they indexed as two different pages? Are they at least condsidered being two different pages from a "machine" view?

(P.S: I am asking because I am going to install disqus comments sistem on such a page and I don't know will the comments be different deneping on different page parameters such as lessonID).