What exactly are drop sets??
When you reduce the weight and with almost no rest continue to perform the exercise. For example dumbbell curls
Do all three weights with no rest. As soon as you hit 8 on the 40s grab the 35s and continue.
In a nutshell:
When you fail at a given weight on a given movement you immediately “drop” the amount of weight so you can continue past failure at the original weight. Double drop sets would have you doing this twice in a set, triple… you get it.
At least that’s the way I learned em. Some people call em strip sets.
The ways it’s done varies depending on the exercise an the equipment being used.