A packet analyzer is a program (or sometimes, a device) that monitors the data traveling between computers on a network. A packet analyzer is also commonly referred to as a network analyzer, packet decoder, network monitor, protocol decoder, or, more frequently, as a packet sniffer. It must be noted that Sniffer is a registered trademark of Network Associates, Inc.
When you plug the cable into your computer's network adapter or dial up your Internet Service Provider, you join a network, which allows your computer to "talk" to many other computers, be it a web server of your favorite search engine, your friend's PC running an instant messenger such as ICQ, or a mail server that stores your e-mail. Just like people, computers need to "talk" to exchange information. That's what your computer does almost every second that you are online. The last time that happened was only a few seconds ago, when you downloaded this page from our web server.
Again, just like people use different languages and dialects to exchange information, computers converse using "protocols," which are mutually agreed standards that allow computers to "understand" each other. The problem is that computer conversations usually look like random binary data. That's why you need a packet analyzer: It decodes network traffic, makes sense of it, and performs many other interesting functions.
