Scientist everywhere - from NASA and universities to inventors in the garage - are using online video to explain their theories and knowledge. Online video is an ideal medium to bring scientific ideas to the masses. With some creativity, animation software (or just a whiteboard) complex theories can be broken down into understandable nuggets.
With all of these science videos online, students have access to hundreds of teachers, each with a different style and approach. If you don't understand a concept as explained by your text book or professor, just go to YouTube and you'll most likely find a video that explains it in a way you will understand.
To learn more about how and why scientists are embracing online video, check out this article from ReelSEO. For more videos, here's a list of the top educational video sites online.