In order for different computers to communicate with each other they must both speak the same language. The rules for these languages are called Network Protocols.
A protocol describes how a packet of information is organized and the rules it follows when traveling across the network.
There are many different types of protocols and this can cause a lot of confusion. In general network protocols can be grouped into three general catagories: lower level protocols, upper level protocols and application protocols.
Lower level protocols are sometimes called hardware protocols or even physical level protocols and are generally related to a network media. Examples of lower level protocols include Ethernet, IEEE 802.3, ATM, Token Ring and Frame Relay.
Upper Level Protocols are sometimes called software protocols are