I don't know if the statement above is 100% accurate: as a matter of fact Power Automate Service lets you create scheduled cloud flows that call an attended Power Automate Desktop flow!
So clearly your general statement "Scheduled is unattended" is not an accurate statement imo.
I only very recently started looking into Power Automate (Desktop) and I found it difficult to unterstand the meaning of attended vs unattended from a technical and from a licencing point of view.
I appreciate the intention to help, however I must honestly say that short (and inaccurate, or at least far too generic) answers like the one above are counter productive when wanting to clarify confusing terms/restrictions and licences. And they do not provide any value for future reference for users having the same question. And finally, posting two quick sentences that do not touch upon the use case explained(!) in any form and are just a very vague summary of Microsofts already vague explanation may only be pushing ones post count up very quickly. I often get the impression that this is the sole purpose.
After doing some further research I think it comes down to that:
Microsoft (and the answer above) state that attended flows "requires human intervention". I think this is irrelevant. My flow runs perfectly fine without "intervention" or human input! It can run every day at the same time automatically. The crucial part seems to be that for an attended flow to run, the machine performing the desktop-flow needs to be unlocked and the user that owns the flow needs to be signed in!
Whereas unattended flows will sign-in themselves to a machine to perform the flow and afterwards sign out again.
So "human intervention" seems to be an euphemism used by Microsoft - what they really should say (and what would bring some clarity!) is: "if you want your flow to run automatically without having an unlocked machine 24/7 posing a security risk, you have to pay $150 ("Per-user plan with attended RPA" plus "unattended add-on") on top!"
