A protocol is a standard set of rules that governs how computers communicate with each other.
Protocols describe both the format that a message must take and the way in which messages are exchanged between computers.

Protocols enable different types of computers (Macintosh, PCs, UNIX, etc.) to communicate in spite of their differences.

This is because they describe a standard format and method for communicating.

The internet family of protocols:

• TCP / IP:Transmisson Control Protocol / Internet Protocol -The parents of the family
  
• SMTP: Simple Mail Transfer Protocol – used for sending mail
  
• POP: Post Office Protocol – used for retrieving mail
  
• FTP: File Transfer Protocol – used to upload and download files
  
• HTTP: Hyper Text Transfer Protocol – protocol used to transport web pages
  
• LDAP - Lightweight Directory Access Protocol - is built on the X.500 standard and allows applications to obtain directory access and information.