The theory is: if you remove the lower buds, you'll get larger, more potent bud from other sites. Most evidence of this is anecdotal, but the majority of home growers swear by it so it's still compelling. The drawback to this is that the lower bud is great for making hash or edibles. Oddly enough, your weakest buds make your most potent product. You'll have to decide what you want. I just lollipopped for the first time to put it to the test.