Definitions List:

Meta Crawlers/engines: launches other search engines e.g., dogpile, profusion
Search Engine: any agent that either spiders (searches) the web looking for info or uses other agents (meta engines.)
Portal: the sort of place that people use as a homepage for more than searching e.g., yahoo, netscape. Usually the site has more information than a search engine like pages, groups, games and news.
Link Weight: rates sites on the basis of how many other sites link to it plus the link weights of those sites
Crawlers: agents that crawl (spider) the web
Editor Based Service: not automated but each site is reviewed by an actual human being (or geek) e.g., Open Directory
Open Directory: the largest and most important editor based service - it is an open source free collaborative - you too could be an Open Directory editor.
Meta Engine: see meta crawler