What exactly is it?

Well, first of all, it stands for "Model-View-Controller". Second of all, it is not a thing, but rather a concept. A concept in which the logic is separated from the user interface, meaning that the programming part is separated from the design (model being the programming part and view being the design part).

To make it easier to understand, the programming should never be mixed with the presentation, to make it easier to change the design when needed, without affecting the way the system works - therefore resulting in less bugs and much more flexibility.

Model-view-controller - Wikipedia, the free encyclopedia

__________________