SEO Dictionary5:

SEO Dictionary5:

Crawler
Also known as Spider or Robot, a crawler is a search engine program that "crawls" the web, collecting data, following links, making copies of new and updated sites, and storing URLs in the search engine's Index. This allows search engines to provide faster and more up-to-date listings.

Delisted
Also known as banned or blacklisted, a delisted site is a URL that has been removed from a search engine's Index, typically for engaging in Black Hat SEO. Delisted sites are ignored by search engines.

Description Tag
Also known as a meta description tag, a description tag is a short HTML paragraph that provides search engines with a description of a page's content for search engine Index purposes. The description tag is not displayed on the website itself, and may or may not be displayed in the search engine's listing for that site. Search engines are now giving less importance to description tags in lieu of actual page content.

Directory
A directory is an Index of websites compiled by people rather than a Crawler. Directories can be general or divided into specific categories and subcategories. A directory's servers provide relevant lists of registered sites in response to user queries. Directory Registration is thus an important method for building inbound links and improving SEO performance. However, the decision to include a site and its directory rank or categorization is determined by directory editors rather than an Algorithm. Some directories accept free submissions while others require payment for listing. The most popular directories include Yahoo!, The Open Directory Project, and LookSmart.