Ping is the name of a computer network tool used on TCP/IP networks. It provides a basic test of whether a particular host is operating properly and is reachable on the network from the testing host. Ping provides estimates of the round-trip time and packet loss rate between hosts. It works by sending IMCP "echo request" packets to the target host and listening for replies (ICMP "echo response" packets).
Ping can be used for several purposes:
to ensure that your domain resolves correctly
to ensure that your server is on line and able to answer IMCP "echo requests"
Being able to "ping" your domain does not mean that other services are accessible.