I can't find an answer to this anywhere, not even in the QFT texts themselves.
I asked a similar question here. Maybe this helps.
This may help
"Physicists use fields to describe the things that don't just have a particular position, but exist at every point in space. For example, you can think about the temperature in a room as a field- it may be different near an open window than near a hot stove, and you could imagine measuring the temperature at every single point in the room."
-String Theory for Dummies by Andrew Jones
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