Ping sends a packet to a remote or local host, requesting an echo. If the echo is returned, the site is up. If the echo is not returned, it can indicate that either the site is down or there is some sort of network trouble along the way.
What you will need to know: the IP address - in either numerical or mnemonic format. Example: COMPUSERVE.COM or 184.108.40.206.
Example of reliable Ping output:
ping access.iac.net little-miami.IAC.NET is alive
Example of unreliable Ping output:
ping not.real.com ping: unknown host not.real.com
If you see either an unknown host error, chances are the network is either unstable or the host name does not exist. If you see a "100% packet loss" error, the network at the remote site could be down or unstable.