Throwables are easy to use. At any time during gameplay, simply click on the symbol next to your avatar that looks like a hand holding a ball. Your list of Throwables. Click your desired Throwable and then click an opponent to launch it their way.
In layman's terms, the bubble is the moment in a poker tournament where one more player must be knocked out before all remaining entrants are in the money. The potential of getting so close to cashing but falling at the final hurdle can cause players to act very differently on the bubble.