heisenberg uncertainty principle - What is meant by "Nothing" in Physics/Quantum Physics?

I am not a phycisist, so please forgive my ignorance. This is related to my posts and this.
I am trying to understand what is meant by the term "Nothing" in physics or Quantum Field Theory (QFT) since it seems to me that this term is not used in the way we understand it in everyday language.

So QFT seems to suggest (in a nutshell) that "things pop out of nothing".
But from wiki I see the following quote:

"According to quantum theory, the vacuum contains neither matter nor energy, but it does contain fluctuations, transitions between something and nothing in which potential existence can be transformed into real existence by the addition of energy.(Energy and matter are equivalent, since all matter ultimately consists of packets of energy.) Thus, the vacuum's totally empty space is actually a seething turmoil of creation and annihilation, which to the ordinary world appears calm because the scale of fluctuations in the vacuum is tiny and the fluctuations tend to cancel each other out.

So what is "Nothing" in QFT? If this quote is correct, I can interpret it only as follows:
The "Nothing" is not in the way used in everyday speech but is composed of "transitions" i.e. something that is "about to become"
Is this correct? If yes, why is this defined as "Nothing"? Something that is "about to become" is not nothing but there is something prerequisite.
In very lame terms: Einstein was born a non-physicist but became a physicist, so if this is a correct analogy, then there

1. there is something underlying that was non-something that became something


2. A non-something came into something because something else (not nothing) permitted it to become. E.g. Einstein's talent (or Mozart's) would have been lost had he been born in Africa or in a country with no educational facilities. So he would not become a physicist (but the required talent would be present but not come into reality)

Could someone please help me understand this (perhaps trivial to you) concept?

Answer

In Physics "nothing" is generally taken to be the lowest energy state of a theory. We wouldn't normally use the word "nothing" but instead describe the lowest energy state as the "vacuum". I can't think of an intuitive way to describe the QM vacuum because all the obvious analogies have "something" instead of nothing "nothing", so I'll do my best but you may still find the idea hard to grasp. That's not just you - everybody finds it hard to grasp.

Start with the classical description of an electric field (Maxwell's equations). It's not too hard to image an electric field as a field filling space. You can even feel the field: for example if you put your hand near an old style TV screen you can feel the static electricity. You can imagine turning down the electric field until it disappears completely, in which case you are left with the vacuum i.e. nothing.

Now imagine the same field, but this time we're using the quantum description of the field (Quantum Electrodynamics instead of Maxell's equations). At the classical level the field is approximately the same as the description Maxwell's equations give, but now we have fluctuations in the field due to the energy-time uncertainty principle. Just as before, imagine turning down the electric field until it disappears. Unlike the classical description, the (average) electric field may disappear but the fluctuations do not. This means the quantum vacuum is different from the classical vacuum because it contains the fluctuations even after you've turned the field down to zero.

The key point is that when I say "turn the field down" I mean reduce the energy to the lowest it will go i.e. you can't make the energy of the electric field any lower. By definition this is what we call the "vacuum" even though it isn't empty (i.e. it contains the fluctuations). It isn't possible to make the vacuum any emptier because the fluctuations are always present and you can't remove them.