Start Time is the time from start of 1st request until the start of this request.
End Time is the time from start of 1st request until the end of this response.
Latency is the time from end of this request until the beginning of download of this response.
Response Time is the time from start of 1st request until the beginning of download of this response.
Duration is the time from start of this request until the end of this response.
Every modern web browser includes a powerful suite of developer tools. These tools do a range of things, from inspecting currently-loaded HTML, CSS and JavaScript to showing which assets the page has requested and how long they took to load. This article explains how to use the basic functions of your browser's devtools.