'Passive income' is the most oversold phrase on the internet.
A working definition, an honest list of what actually qualifies, and the three things that don't but get sold as if they do.
Passive income is money that keeps arriving with no marginal hour of your time. That's a short list: dividends, interest, royalties on work already done, a rental with a real property manager. That's basically it.
Everything else on the internet marketed as 'passive' — the course, the affiliate site, the print-on-demand shop, the short-term rental you self-manage — is a small business. It might be a good small business. It is not passive.