Latency is the elapsed time between sending a request and receiving a response. For interactive applications, lower latency generally feels more responsive. A browser-based measurement includes network transit plus endpoint and browser processing, so it may be higher than a raw ICMP ping.
Why it matters
Gaming, remote desktops and voice/video calls are sensitive to delay. Large downloads depend more heavily on throughput.
What affects it
Physical distance, routing, congestion, Wi-Fi interference, cellular scheduling, VPNs and server response time can all add delay.
How to troubleshoot
Compare Wi-Fi and Ethernet where possible, test without a VPN, move closer to the access point, avoid saturated uploads, and compare multiple endpoints.