Passive income is an income received on a regular basis, with little effort required to maintain it. It is closely related to the concept of "unearned income".
Today there is really so many business opportunities out there and we can really leverage the use of "passive income" to work smarter.
This can be in means of a membership site or a service plan. There are hundreds of different ways to create substantial passive income. What is nicer is having 3 or 4 passive incomes at once and building them all at the same time with just one website.