1. Fast thinking neural nets (emotions), systems that integrate sensory signals and put out a signal that indicates something else. We can't 'see' inside these systems, we can only believe their outputs are appropriate or not.
2. Slow thinking memory that uses language and ideas to make estimates and calculate future possibilities.
3. You. The thing that decides what to think about.
We know almost exactly how systems 1 & 2 work. We've given out several nobel prizes for these topics. We reproduce them in the lab and we make them better every day. We use artificial versions of them to make our lives easier every day. (Have you used Google search lately?) And they'll continue to get smarter, faster and more reliable.
We also recognize that system 2, which relies on language, is what makes us most diffrerent fromt he rest of the species on this planet.
However, we have little idea of how system 3 works. Maybe that's best. If we don't have a system 3 then we don't have to worry about the systems 1 & 2 becoming 'super intelligent' and taking over the world. They remain black boxes that can 'think' faster than we can, but have no motivation.
Thanks for reading,
 Thinking, Fast and Slow, Daniel Kahneman, published by Farrar, Straus and Giroux; Reprint edition (April 2, 2013)