The features module enables the capture and management of features in Drupal. A feature is a collection of Drupal entities which taken together satisfy a certain use-case.
PURL 1.0-beta6 requires CTools. Please make sure you have added it to your modules before running update.php.
PURL (pronounced 'perl') stands for Persistent URL. PURL is an API module -- it is meant to be a helper (and one that does some heavy lifting at that!) for other modules interested in using elements of the page request to sustain information between pages without using a SESSION or other hackish means.
Translation: PURL does absolutely nothing for the end user out of the box without other modules that take advantage of its API.
It is an API module that provides a way for other modules to take advantage of concepts using custom_url_rewrite_outbound() without having to write the complex logic that URL rewriting often requires. An example implementation of this API can be found in the spaces module.