A client is any application that "connects" to a server or service. For example, check out some of the most popular clients that almost everyone uses on a daily basis:
| Email Client | Web Client | IM Clients |
Apple's Mail Thunderbird Entourage Eudora Outlook |
Apple's Safari Firefox Explorer Opera Camino Netscape |
Apple's iChat AOL Instant Messenger MSN Messenger Adium |
What makes these applications "clients" is the fact that in order for them to be useful at all, they need to connect to another computer which serves them information. Other kinds of clients may be a Bit Torrent client or a Newsgroup client or an FTP client.