Guard rail
A guard rail is a rule that stops an AI or an app from doing something unsafe or off topic.
In a simple example
A shop assistant is blocked from promising refunds, and it must pass hard questions to a person.
Why it matters to you
Rails keep a helpful tool from costing you money or damaging your name when something goes wrong.
Do not confuse with
A guard rail is a rule built into the tool. A polite request in a prompt can be ignored; a real rail cannot.