Intuitive
Explanations in this section should contain no formulas, but instead colloquial things like you would hear them during a coffee break or at a cocktail party.
Concrete
In this section things should be explained by analogy and with pictures and, if necessary, some formulas.
Abstract
The motto in this section is: the higher the level of abstraction, the better.
Why is it interesting?
The Heisenberg equation describes the time-evolution of observables in quantum mechanics.