[ncmncm]

This is more helpful than anything I have ever encountered on the topic.

Comments:

1. It should explain map somewhere before it is used.

2. For the more abstruse and abstract concepts, a comment suggesting why anybody should care about this idea at all would be helpful. E.g., "A is just a name for what [familiar things] X, Y, and Z have in common."

3. It goes off the rails halfway through. E.g. Lift.

[sanderjd]

Expanding on your #1, I think they could use some more definitions. As you say, they use "map" in its functional programming sense before defining it, but I think more confusing is this one:

> A category in category theory is a collection of objects and morphisms between them.

What is a "morphism"?

I think this is a great starting point though, which could use some expansion.

[ncmncm]

Ja, that "morphism" bit matches my #3.