File Transfer Protocol (FTP)
FTP is used to transfer files between computers. 
FTP client connect to remote FTP server list shared files, upload or download files .
FTP runs over TCP
Ex: FileZilla

SFTP (Secure File Transfer Protocol)

SMTP (Simple Mail Transfer Protocol)
Electronic-mail protocol for sending a mail from one server  to another server. 
SMTP server has a DNS (MX record) that refer to the domain to receive mail .

Post Office Protocol (POP)
POP protocol used by local e-mail clients to retrieve e-mail from a remote server over a TCP/IP connection. Current version is POP3. 

Mail clients are configured with the address of a POP3 server to receive mail and the address of an SMTP server to send mail. POP protocol is being replaced by IMAP.

Telnet
Provides a virtual terminal to access remote servers 
Telnet logs you directly on to the remote host,

SSH (Secure Shell)
SSH is a program for logging in to and executing commands on a remote machine with secure encrypted communications. 

SSH provide better security.
Online SSH client

Point-to-Point Protocol (PPP)
PPP used to establish a direct connection between two nodes. 
PPP can provide connection authentication, transmission encryption and compression. 
PPP is used in serial cable, phone line, trunk line, mobilephone, radio links, fiber optic and Internet access. ISPs use PPP to provide dial-up access to the Internet. ADSL use POP Ethernet protocol.