Latency is usually measured in milliseconds (ms) and is a measurement of delay and measures the time it takes for data to get to its destination.
Latency is usually measured as a round trip delay in the time it takes the information for your device (like clicking on a link) to get to its destination and back again. During broadband speed tests, it’s referred to as a the ping rate.
When delays in transmission are small, it is referred to as a low-latency network (good) and longer delays are called a high-latency network (not so good).
A good ping (latency) is 60ms or lower but latency is also dependant on how far the destination is from the source. For example, latency (Ping) for a connection from London to France will be less than London to India because of the distance the information has to travel.