As jasonlotito points out I mean that after the initial investment, i.e the creation of the product or system, you will generate money with little to no involve

As jasonlotito points out I mean that after the initial investment, i.e the creation of the product or system, you will generate money with little to no involvement. You're likely going to have a few hours work a month with most passive income streams but the point is, after development, you generate money without focusing on it. For example: I created a simple iOS app that netted ~50k users. It generated about £1k per month and the only work I needed to do on it was answer a few emails a month. You pointed out in your comment the example of people selling physical products on Amazon. I know several people making the majority of their income, passively, from that. So your 'it's also not making them much money' comment, which you failed to back up, is wrong. It's possible. For most people passive income doesn't need to be very much, just a nice little supplement to their salary. For others it can be their entire income and more than enough to live on.