It's the (convenient) practice of storing your waste in bottles. There are several benefits to this. First, doing so means you don't need to leave your room/computer every time you get the urge to pee. Anybody who spends a fair time at the computer would be able to understand how nice bottling makes things.

Second, it's also kinder to the environment. Most people flush every time they pee, even though they only release a miniscule amount of urine, yet every flush uses up about three gallons of water. Think of how many times a day you stop into the bathroom to pee and you'll understand just how much water is being pointlessly wasted.