Paths
By default Drupal assigns each page a path (web address) like: http://www.example.org/node/1
Pages are numbered in the order they were created.
Pages can receive fancier URLs
Your Drupal site will automatically create a URL alias (non-numerical path) for each page like: http://www.example.org/your-page-topic
URL aliases are more visitor- and search engine-friendly than numerical paths.