If your jungler is willing to start red/blue without a leash, then the strat is for the support to tank gromp/krugs while the ADC takes it (and claims all the exp). This allows the ADC to walk into lane already level 2 when everyone else in lane is still level 1. Depending on how fast you clear the camp and whether or not the jungler wants to toss you his smite, you can still clean up most of your wave and hit level 3 when everyone is still level 2. This early level advantage can give you easy lane dominance and maybe an early cheese kill if you play it right since you'll have access to an entire extra skill and level stats on your opponents for the first 3 levels.
I wouldn't try it if you're not planning on making use of it (especially in SoloQ), since if you get nothing out of it if you play the lane relatively the same, the end gain/loss value is your jungler getting a subpar start in the jungle just so you can get 2 pots worth of gold.
If they're simply not leashing, and the jungler doesn't need one to avoid staying behind, then the idea is to get to lane before the enemy and rush level 2 so that you can commence the same cheese kill/lane dominance. The only difference is taking the camp guarantees you level 2 walking into lane unless the support takes exp, and even then you'll still have a slight exp boost to hit lvl 2 sooner as long as you dont miss too much of the wave.