Ping is simply the time it takes for you to send a packet (A packet contains a small portion of the internet content you request; You receive many packets to get all of your content) to a remote network device and then receive a response back. You want ping to be as low as possible. However, the farther away the server is that you are trying to reach, the longer the ping will be since there are physical limitations on how fast network traffic can travel. Additionally, the number of network devices between you and the server will increase the time as each router/switch has to determine where the packet should go next. A ping of 17 milliseconds is quite low, but it depends on how close you are to the server.
The download speed is how...