Here is a clearer description of what I posted earlier:

Both SSH and Telnet are basicly the same, you have a text-base interface which you can type commands. The difference is that ssh is encrypted and telnet is not. When you are using telnet to access a system, the entire connection — including your password, all commands you type, and all email you read and send — travels in cleartext and can be easily intercepted and read by a malicious user (man-in-the-middle). With ssh, all of your passwords and data are encrypted first through a secure process that is much less sesceptible to eavedropping and interception.