Here's a link to a page from the Documentation section that explains some things about pages:
They are a little like "static" posts, but more like separate web pages that you might want to use for other kinds of site information. While you'd usually use an input/editor similar to the one used when typing posts, you can also switch
that to an html editing view to do some html sorts of things, if you are so inclined. To get to pages, you'll probably want to either design a link in your theme for that (that would be in the site.master of your chosen theme), or you might want to use
the pages widget or link list widget to help people navigate to them.
Al Nyveldt has an interesting post about using "the other kind" (i.e., separate .aspx files) of pages in various ways in your site:
but note when you add a "page" through the "pages" control in the administrative interface, it's adding a bit of html to a database field, not actually writing a separate file on the disk.
If you're planning to use some asp.net control on the page--like a gridview or a submit button or something, you'll want a "file-based" kind of .aspx kind of page. If you want to post information and maybe an image, a wysiwyg-edited "put
text in the database field" kind of page will probably do.