A protocol is a set of rules which is used by computers to communicate with each other across a network.A protocol is a convention or standard that controls or enables the connection, communication, and data transfer between computing endpoints.
On the Internet the set of communications protocols used is called TCP/IP. TCP/IP is actually a collection of various protocols that each have their own special funtion or purpose. These protocols have been established by international standards bodies and are used in almost all platforms and around the globe to ensure that all devices on the Internet can communicate successfully.
There are a variety of protocols currently in use for wireless networking. Arguably, the most prevalent is 802.11b. Equipment using 802.11b is comparitively inexpensive. The 802.11b wireless communication standard operates in the unregulated 2.4 Ghz frequency range. Unfortunately, so do many other devices such as cordless phones and baby monitors which can interfere with your wireless network traffic. The maximum speed for 802.11b communications is 11 mbps.
The newer 802.11g standard improves on 802.11b. It still uses the same crowded 2.4 Ghz shared by other common household wireless devices, but 802.11g is capable of transmission speeds up to 54 mbps. Equipment designed for 802.11g will still communicate with 802.11b equipment, however mixing the two standards is not generally recommended.
The 802.11a standard is in a whole different frequency range. By broadcasting in the 5 Ghz range 802.11a devices run into a lot less competition and interference from household devices. 802.11a is also capable of transmission speeds up to 54 mbps like the 802.11g standard, however 802.11 hardware is significantly more expensive.
Another well-known wireless standard is Bluetooth. Bluetooth devices trasnmit at relatively low power and have a range of only 30 feet or so. Bluetooth networks also use the unregulated 2.4 Ghz frequency range and are limited to a maximum of eight connected devices. The maximum transmission speed only goes to 1 mbps.
There are many other standards being developed and introduced in this exploding wireless networking field. You should do your homework and weigh out the benefits of any new protocols with the cost of the equipment for those protocols and choose the standard that works best for you.