I recently came across the channel of Gerald Undone who has very succinct but detailed explanations of complex technical issues in photography. If you don't understand them after watching his videos, you are probably beyond salvation.
I have selected some, and there are probably more in his channel.
I was particularly intrigued by the depth of field explanation, which says that it is the same regardless of focal length, but the bokeh looks more pleasing in high focal length lenses because they also magnify the out of focus area in the photo, along with the subject.
The one about crop lenses was also enlightening, and it explains how speed boosters work.
And finally here is one on white balance. It allows you to detect the photographers who really care about it, because they wear something grey on their wrists.