No matter how experienced of a musician you are, you can definitely understand what harmony is in this video. The video first starts off with Jacob Collier, a musician and composer, giving the simplest definition of harmony - a bunch of notes being played together to sound nice. Collier than goes on to explain harmony on different levels given the depth of his audience's understanding of the term. Eventually, he converses with a famous jazz musician and song writer, about the different chords that can be used and how to use them.
This video, although the explanations can feel a little rushed in the higher levels, can help those learning jazz and can draw some inspirations from what is being discussed in this video.