Open a command-prompt and type "telnet".
Your machine will have one I'm sure.
whenever i'm trying to open it there is a error message saying that "it's not a valid win 32 application". Plz help me with this
Open a command prompt and type "telnet" (no " though) - see what that does. What do you want it for? - not a great deal of use these days. L
Telnet is the computer equivalent of morse code i.e. there are way more efficient means of connection (such as SSH)
Wikipedia should be able to tell you what telnet is (basically it's a type of internet communication protocol). As for what version you'll need, probably the latest version. What you need isn't so much a 'version' of telnet as it is a telnet client. (Similarly, you would want an email client moreso than the latest version of email). For Windows, a popular telnet client is PuTTY, while the built-in OSX Terminal application will allow you to make telnet connections on the MacOS X computers.