Category Theory – "CT" from here on – is the study of transformations, in a general sense. A very general sense. It has been called "thinking with arrows," because whenever CT folks

As additional support for my previous post on functors, I want to throw in this less technical example. As you can see in the drawing, we have the following: A little world of transformations between things

Everything in the universe can be thought of as "a box" if you try hard enough. A computer is a box of interconnected electronic thingies. A pizza is a disc-shaped box of... a bunch of stuff.