Wouldn’t it be nice to earn money while not working? That money is called residual, or recurring, income. It's what can happen after you put a lot of time, effort and sometimes money into a job to continue to get paid for the work months or years after it's done. (Salary jobs are part of linear income. This income is directly related to the number of hours you work. If you work 40 hours, you get paid for 40 hours of work.) Once you set up your business to earn residual income, you continue to make money while doing other things – maybe even starting a new business to generate more residual income!
Active income, on the other hand, involves earning money in exchange for a service. It could be a salary, an hourly wage, commissions, or tips. It’s essentially a trade of your time for a fixed dollar amount. Most people choose to live this way, and there’s nothing inherently wrong with that, as long as you understand that there will be a limit to how much money you can realistically earn.

Mike, I don’t consider the income from FS to be passive, as I’m spending time commenting to you right now. But since 75% of my traffic comes from search, the most traffic I would probably lose is 25% for probably a year. And then my search word rankings would probably slowly fade given frequency of posting new content is one of the search algo variables.
Owning property can earn you passive income for decades to come. Once you purchase a duplex, home, or apartment building as a rental property, you’ll earn a consistent monthly income with little work. Rent should cover your mortgage, taxes, repairs, and other expenses. You’ll continue to earn income by paying off your mortgage with the rent money and saving excess rental income.
If you're looking to get started in real estate, look at a crowd funding solution like RealtyMogul. It works similar to LendingClub - you commit as little as $5,000 towards a property. When the property is fully funded, you become an owner, and will receive your share of the earnings and appreciation in the property.  Check out RealtyMogul to learn more.