The Pintsize theme is a minimal working theme and because of its size can be broken down into easily understandable code chunks. There are some commonly used template files that are missing in Pintsize. Some of these are 404.php, archive.php, comments.php, search.php and searchform.php. If you look at the Template Hierarchy chart, you will see that 404.php, archive.php and search.php all default to executing the code in indx.php if they do not exist in the theme. The template file comments.php is used to process comments on a page and the template file searchform.php generates the search form.
My efforts barely scratch the surface of the WordPress World, there is plenty left to explore but one must begin somewhere. I hope that this series of articles is of use to you. Let me know…