A ping test sends a small packet to a remote server and measures the round-trip time. It's the single best indicator of how responsive your connection feels, far more so than the headline Mbps number.
Ping (latency) is the number of milliseconds it takes a packet to leave your device, reach a server, and come back. It's bounded by the speed of light in fibre, so distance matters: London to Sydney can never be faster than ~140 ms regardless of how good your connection is.
Jitter is how much your ping varies between consecutive measurements. A connection with 20 ms ping and 1 ms jitter feels solid; one with 20 ms ping but 30 ms jitter will stutter on calls and rubber-band in games.
Packet loss is the percentage of packets that never arrive. Anything over 1% on a wired connection is a real problem. On mobile, up to 1% is normal in weak coverage; over 3% will make video calls drop.
Our engine sends 12 small HTTP requests to Cloudflare's nearest edge after a TCP/TLS warmup. We drop the worst 20% of samples to remove outliers and report the average for ping and an RFC 3550-style mean absolute deviation for jitter.