It’s a test that measures your ping.
Ping measures the minimum required time to send echo request packets from you to our servers and back to you. It’s calculated in milliseconds and shows us whether you will have delays in response from the servers. So the smaller ping is, the better Internet connection you have.
The higher ping you have, the bigger delay you will experience while making actions in a game, which is critical for online games. Example: Imagine yourself playing Call of Duty. Your target is on the move. You make a shot, but while the signal from your computer goes to the servers and back, your target has already moved a few meters away from the place you shot. Ugh! If you ping is high you will probably not enjoy your game.