Napster and Gnutella
Unlike an Internet search, Napster searches do not search the World Wide Web; instead, they search Napster's database, and allow you to retrieve the files from users' computer hard drives using a modem or other connection device. Searches using Gnutella do the same thing, except they don't require a central server.
To use Napster, you must first download their software from the Napster (or Macster) Web site. You can then send a search request to Napster's central server, where a massive list of all the songs on other Napster users' computers is stored.
Napster returns a list of other users with the file on their hard drives, along with the speeds of their connections. From there, it's as simple as point-and-click: Choose the file you want to download, and in a matter of minutes it's sent directly from the other user's hard drive to your own, without traveling through the central server.
Unlike Napster, which is called a "client-server" model because users, or clients, connect to the central server when they search, Gnutella links its users directly to other users in a "distributed network" of computers with no central point of control. In this model, every Gnutella user acts as both a server and a client -- a server when he or she sends out information, and a client when he or she retrieves information from another user's computer.
To perform a search on Gnutella, a user links his computer (via modem, DSL , or whatever) to another user's computer, called a "servant." The second computer in turn contacts all of the servant computers it has ever been connected to, and those computers contact all the computers they have ever been connected to. The network is similar to a chain letter: One person sends a message to another person, who sends that message to 20 other people, and so on -- until the search request has been sent to everyone on the Gnutella network.