This measured how much time it takes to do any particular task. This is also called response time and is the time it takes to get a response to the client.
Improving Latency
A good way of writing faster code is by improving single-threaded performance but there is a limit to how much you can improve single-threaded performance. Any improvements here may also help with the parallelized version. On the other hand, faster sequential algorithms may not parallelize as well.