Whenever there is a link on the internet that points toward a specific web page, that pages Page Rank is increased (with the exception of nofollow links). The amount it increases is determined by the Page Rank of the web page that is pointing to it, and a few other things that we won't go into. A link from a site with a Page Rank of 0 will not do much to boost a web pages Page Rank, but it will boost it a tiny bit. A link from a site with a Page Rank of?5 however would instantly raise that web pages Page Rank to a much higher level.
This tutorial will be focusing on obtaining external backlinks from other website in order to increase the Page Rank of a specific web page of yours. Internal links are only really of value if you own a site that has some Page Rank already (you can't simply link 100 pages of your own site to a specific web page on the same site and hope to achieve any results, unless those 100 pages have any Page Rank of their own).
You can find out a pages Page Rank by using the Google Toolbar, downloadable here: http://toolbar.google.com