Essentially, there are multiple different ways in which we can attribute a certain task to other tasks or to the party that initiated it.
Those different ways are not always obvious, because for the straightforward case, they all kinda give you the same answer. As a result, it took me a while to wrap my head around their differences, and I’m hoping to save someone some time by outlining them.
"First Input Delay (FID) measures the time that it takes for a web page to respond to the first user interaction with the page. As of July 2018, FID is available in the Chrome UX Report as an experimental metric."