On the same note, I recently shared a link[0] to his great beginner talk on functional programming languages. This was by far the best introduction to monoid, monads and few other functional programming terms.

Direct youtube[1] for those who don't want to click twice :)

[0]: https://news.ycombinator.com/item?id=25571001

[1]: https://www.youtube.com/watch?v=Nrp_LZ-XGsY