Before getting into quantum field let us first talk about the field, so a field is any quantity which measures pretty much all the points in space and now this quantity could be a scalar quantity like electrical potential or a vector quantity including tensors. If we talk about an electromagnetic field. it’s actually made up of two fields, an electric field, and a magnetic field or in simpler words, we can say that we UNIFY them.
likewise, a quantum field is a Quantum measurement assigned to every point in space. If we step down from an electromagnetic field to an energy field. Quantum properties are intertwined with each other through a wave function and if we imagine the quantum properties to be a part of fundamental fields, then they no longer would be attached to the particles.
There are total of 17 different elementary particles with unique properties and are they are as:
some of those properties are fixed and others are unpredictable like spin orientation etc, we’ll be needing around hundreds of fields if we start treating these properties as a field but we might group them together as we did with the electromagnetic field. The basic quantum numbers we have are the spin, electric charge and color change. we can distinguish gluons from photons on the basis of color change. so if we make groups using such strategy so we get 37 fields instead of hundreds of fields, so we’ve got six Leptons, 6 Quarks each with 3 possible color-charges, 8 color charge distribution for gluons, 1 photon, 3 week Bosons, and 1 Higgs.
The existence of field everywhere in space time doesn’t really mean that the particles are everywhere. We only get a particle when Quantum field gets excited.
Quantum field theory model tells us how the quantum field interacts, so a quantum field is a set of quantum properties assigned to every point in space and each of them existing alongside with others, allowing them to interact and any energy in a field higher than it’s vacuum state will be seen as a particle carrying the properties of that field
just as our physical reality is described by the Quantum field theory, these complex systems are more than just the combinations of these fields put together into some stable or quasi-stable bound state. we can consider this entire universe to be a complicated quantum field, that holds the entire physics. Quantum fields can describe an arbitrarily large number of particles that interact in all ways our theories can conceivably allow. and they do this not in some vacuum of empty space but amidst a background of not so empty space which plays by the rules of quantum field theory too. As we know that particles, Anti-particles and all sort of excitations of the fields are constantly being created and destroyed where the reality must be fundamentally different from the classical picture of a smooth, continuous and a well-defined Universe where the Theory of everything is even much more complicated, and this remains an unsolved problem.