Is it a real phone call or a notification that looks like one?

Short answer: A real phone call over the phone network to your number. It rings, you answer, and a natural voice reads your reminder out loud.

A real phone call, over the phone network, to your number. It's not a push notification styled to look like a call screen — it rings on your carrier line, shows up in your call history, and works exactly like a call from a person: full-screen UI, ringtone, the lot.

This distinction matters more than it sounds:

Delivery path. Notifications depend on the app being alive, Focus modes, battery optimizations and a dozen silent failure points. A phone call depends only on your phone having signal.
Settings. Calls follow ring settings, not notification settings — so no Focus mode or notification summary quietly buries them.
Psychology. Decades of conditioning make a ringing phone the one interrupt people reliably act on. A banner asks for attention; a call demands a decision.

When you answer, a natural-sounding voice reads the reminder text you wrote, word for word. If you can't answer, an SMS backup delivers the same text.