GIF, JPEG, PICT, etc. At the very minimum, a WWW browser must support and read pure text and HTML documents. Most WWW browsers also directly read certain kinds of graphics as well. Browsers usually have a way to interact with other software programs to read and display other kinds of documents not supported by the browser. These other programs are called Helper Applications.
Information is provided by a Server.
The organization name is critical. Gopher is an older protocol that groups and links documents together. Telnet is for establishing a computer session with a host computer. It usually requires a login. Ftp is File Transfer Protocol and is usually used for downloading files.