Addurl term explained
Registration form of the website in the search engine. Each search engine has its own addurl, where you can register the website.
Sending their websites through this form does not guarantee getting a site in the index, as there are many factors which search engines do not add resources to your base. Usually this applies to sites that violate the requirements of search engines, such as: spam resources, doorways, splay and others that do not provide value to visitors and was created for the sole purpose of manipulating search results.
To get into the search engines index it is possible and without the use addurl. It is necessary to place some links to your site from other trust and preferably frequently updated resources.