A red carpet is traditionally used to welcome VIPs such as dignitaries and celebrities at formal events.
More commonly, "the red carpet treatment" and "rolling out the red carpet", refer to any special efforts made in the interests of hospitality.
The earliest known reference to walking a red carpet in literature is in the play Agamemnon by Aeschylus, written in 458 BC. When the title character returns from Troy, he is greeted by his vengeful wife Clytemnestra who offers him a red path to walk upon.