It is used to upload and download files. HTTP is used to view web pages, in the past a protocol named gopher was used. Gopher can't be used to show nice graphics, only text. So HTTP was developed and it s used by almost everybody. Nowadays POP3 is the most favourite standard.
POP is used to receive and read e-mail from a web page.
Telnet sends the usernames and passwords in plain text over the network, so anybody can obtain them very easily by using a packetsniffer. The data transferred between the two hosts is encrypted, so the sniffed packets won't reveal any valuable information. Telnet and SSH are usually used in a UNIX-environment. This layer provides service to the upper two layers, it co-ordinates communication between Presentation layer entities. A session interface and protocol, developed by IBM, which also provides services to the presentation and application layers.