The TCP/IP suite comes with a multitude of protocols, and for either the Network+ exam or the CCNA exam it is a requirement to know their purpose and their associated port number. Here are a few of them.

FTP - (File transfer Protocol) - Port 21 - FTP is a connection oriented protocol at the Application layer, that typically is used to trnafer large files between Unix machines.
FTP Commands Being connection oriented, it utilizes the services of TCP at the Transport layer.

TFTP - (Trivial file transfer protocol) - Port 69- TFTP is the connectionless Application layer cousin of FTP. In essence, it is a stripped down version of FTP.

SMTP - (Simple mail transfer protocol) - Port 25 - This is the Application layer protocol that is used to send email, and move it from email server to email server.

POP3 - (Post office protocol version 3) - Port 110 Post office protocol is used to download email, as we so often do from our ISP. Beware it is in clear text!