The page that displays Posts on homepage

The way you are thinking wordpress is, is not like that. You can’t find the query and alter it like you do in plain PHP. There are filters and actions and a whole architecture to play with pages and posts. I suggest you to read wordpress documentation and Codex.

If you are a programmer then have understanding with PHP and little bit of database then you will be amazed to see the architecture of wordpress.

Suggested Reading:

WordPress Codex

How WordPress Theme Works – by Mashable