In simplest terms, a passive income is generated when you know how much money to invest and where to invest. Continuing with our ‘tap’ example, it means to know which tap to open and by how much. You definitely want to open the faucet that fills up your swimming pool so that you can take a swim in it anytime you want. You definitely do not want to open the tap of your washroom sink, water from which will go immediately go into the drain if not used properly.