Ping is a command used to test whether a host is reachable via your internet connection.
The ping command will need to be run from a Command prompt or terminal depending on your operating system (Windows, Mac or Linux)
Windows:
Use your keyboard shortcuts, press and hold Windows button + R simultaneously and type "cmd" (without the quotes), alternatively simply click on the Start button and typing "cmd" would suffice.
Enter the following command at the prompt:
ping <domain/server> and hit enter, where <domain/server> is the hostname or IP address of the server.
eg: ping domain.tld
Mac:
Open Terminal by navigating to /Applications/Utilities.
In the Terminal window type ping followed by the <domain/server>,
eg: ping domain.tld
CTRL+C to stop pinging
Linux:
Press CTRL+Alt+T simulaneously
Type in ping followed by the <domain/server>
eg: ping domain.tld
CTRL+C to stop pinging
The successes or failures will indicate the out come of the test.
Your next step would be to do a traceroute, and find out where the failure occurs.