URLs are used to point to files online or on a local hard drive. They come in five different formats, file, gopher, news, http, and partial.
File URLs gives users a link to share with their friends, family, and coworkers to a file too large to email.
Jukka "Yucca" Korpela shares information on what file URLs are and how they work.
Wikipedia shares information on the file URL scheme.
U Toronto defines the gopher URL. Gopher URLs are not very common these days because they preceded the web, and most of the gopher servers are no longer functioning.
FreeSoft presents information on gopher URL syntax.
W3 provides more information about the gopher URL syntax. While it may be good to know, it is not very important to use today, because HTTP has essentially taken over gopher.
U Toronto defines the news URL.
News Readers provides more information about the news URL protocol.
Free Download Center provides a tool to grab the RSS feeds of news URLs. This is helpful to organize the RSS feeds of many news sites people use today.
W3 discusses URL protocols—which define the standards for the URLs.
IETF shares a memo with information on the HTTP URL protocol. This is a text document, not a website.
Web Reference provides detailed information on the anatomy of a HTTP URL.
W3 defines and discusses how to use partial URLs.
Partial and Full URLs demonstrates how to use partial URLs to find and open documents that are hosted on the same server.