A Speedtest is a quick procedure that allows you to determine the quality and reliability of your network connection. In simpler words, it helps you to understand how good your internet is.
Three different measurements are taken: latency, download speed and upload speed.
Latency is the delay incurred in processing network data — that is, the amount of time it takes for a packet of data to travel from source to destination. Say, for instance, the time elapsed from the moment you run a query to the instant the results arrive at your screen. Latency is usually measured in milliseconds and the lower it is, the smaller will be the delay times you experience with your connection.
As for the download speed, it refers to the rate at which information such as pictures, music and video is transferred from the internet to your device. The upload speed, on the other hand, is that at which content is transferred from your device to the internet. Both speeds are measured in Mbps.