Passive Income generally refers to revenue you receive that is not directly related to your effort. It also signifies that you are not “materially participating” in a business under IRS guidelines.
As an example, real estate investments can generate passive income for an owner who is not performing real estate services directly, but rather is just investing in the property & someone else is managing it.
Passive income from eCommerce generally refers to selling products or services 24/7 in an automated format so that you have repeated income from sales without repeated direct effort.
There are other types of passive income, but those are two of the most common.