You have a function that does A() and another function that does B().

Upon careful inspection or after just writing/using them 10,000s of times[1] you realize they are both special cases of one general function f()[2]. Congrats, you're likely doing CT now, but barely scratching the surface, though.

Let's say you find a way to do a function factory that generates explicit instances of f() -> A() and f() -> B() at runtime for your different use cases as they are needed. You do this 100 times, 1,000 times[1] with many different functions, in many different contexts. You eventually realize that if all your functions and their signatures had the same structure[3] it would be quite easy to mix some (or all?) of them with each other, allowing you to handle a perhaps infinite amount of complexity in a way that's very clean to conceptualize and visualize. Isn't this just FP? Yes, they're very intimately related.

By this point you're 99.9999% doing CT now, but remember to shower regularly, touch grass etc.

CT formalized these structures with mathematical language, and it turns out that this line of thinking is very useful in many fields like ours (CS), Math, Physics, etc.

1. Which is what happened to me.

2. Which sometimes is a way more elegant and simple solution.

3. This term is fundamental and has way more meaning than what I could write here and what one would think on a first approach to it.