It prevents the light from going on or off when you open the door; allows you to keep it set without auto-shutoff; and doesn't immediately respond to temperature change button presses, and only checks them on a set schedule (this last feature is generally accepted amongst Orthodox Jews as allowed for holidays — "Chag" — but not for Shabbat).

Broadly, yes. You program it beforehand to come on and stay on all thru the day (think of it like a slow cooker), and, ancillary functions, like the light coming on if you open the door, are disabled.