What type of vehicle was the De Havilland Comet, the first of its kind built specifically to carry passengers?

The first commercial jet-aircraft.

The first commercial airliner, with an unfortunately flawed design that led to a series of crashes.

Yes, mozart & Professor and thanks for your answers.

It debuted on May 2, 1952, with a BOAC flight from London to Johannesburg.

DEHAVILLAND COMET

"De Havilland built the world's first jet airliner: the Comet, named for the 1934 racing plane. Fitted with four of Halford's more powerful Ghost jet engines, the Comet entered test flight in 1949 and first carried paying passengers in May 1952. People fell in love with it. Its speed of 480 mph was unrivaled. It flew at high altitude, avoiding discomforts of the weather. Its engines ran smoothly, eliminating the harsh vibration of conventional motors. Orders poured in.

"But during 1954, two Comets broke up in midair. Investigation showed that this airliner was subject to a new and unanticipated type of structural weakness. All remaining Comets were withdrawn from service, with De Havilland launching a major effort to build a new version that would be both larger and stronger. This one, the Comet 4, enabled De Havilland to return to the skies in 1958. By then, though, it was too late. The United States had its Boeing 707 jetliner along with the Douglas DC-8, both of which were faster and less costly to operate. The Comet soon faded, as orders dried up." - CentennialofFlight.gov