Idle is a word that means "lazy" or "hobby". The Idle games are very special games, since your main task will be to click and to make choices. In fact, you collect money or any currency (orbs, minerals, gems, ...) which will help you to acquire new powers, and especially, the reinforcement to work at your place.
Buy a bucket to pick up dollars falling from the sky, a warrior to fight monsters for you, and more. Some games even run on their own, in your absence. The purpose? To unlock all the improvements and to have the immense satisfaction of having completed the ENTIRE game.