To help get an accurate speed reading, disconnect any other devices from your network and stop anything that is using your connection such as automatic updates or backups. If the lights on your modem or router are flickering, that means a device on your network is using your connection which will affect the results.
If you are connected to the modem wirelessly, also run the test with a computer connected to the modem with an ethernet cable to check if your wireless connection is slow.
Download speed is how fast you can receive data. A higher download speed means more people can stream videos at the same time and at a higher quality.
Upload speed is how fast you can send data. It is important to have a high upload speed for online gaming and for making video calls.
Ping, or latency, is the round trip time to send data and receive a response from a server. If this is more than 50 milliseconds, there will be noticeable delays in online gaming, voice over IP (VOIP) calls, and video conferencing.
Jitter is variation in latency over time and typically under 5 milliseconds on a stable connections.
High latency can occur when a device on the network is uploading at a high speed, using all the available bandwidth. This indicates that the router is affected by bufferbloat which can mitigated by limiting the speed of the upload, by adjusting the router settings, or by upgrading to a router without the issue.