(Use the “Full screen” button on the video player to make it bigger)
Look at the left hand part at measure 21. You’ve got stems pointing up and down on the same staff. Composers write this way when they want you to do two things at once with the same hand. In this case, I want you to hold D and F, while you continue to play B-flat on the beat. These two ideas are shown with different colors in the video, but you still play them with just your left hand.
Another unique marking comes at measure 72, where you have 8va and then a dotted line over the right hand part. This is what composers write when they want you to play something one octave higher.