A red carpet is a traditional way to honor someone who's a celebrity or an otherwise distinguished person. Before the Oscars ceremony, people huddle around the red carpet to check out the stars in their fancy tuxes and gowns.
Red carpet is also an adjective meaning "hospitable" or "ceremonious:" "Let's give Grandma the red carpet treatment when she visits!" Hotels often use this term as well: "We roll out the red carpet for our guests." Literal red carpets are commonly used at movie premieres, awards ceremonies, and during the arrival of visiting queens, prime ministers, popes, and other dignitaries.