Space Shuttle Columbia disintegrated as it reentered the atmosphere

What happens in this video ?

On February 1st, 2003, the space shuttle Columbia disintegrated during its re-entry into the atmosphere. The seven astronauts were killed.
82 seconds after the launch of shuttle (STS-107), a sizable piece of foam struck the leading edge of Columbia’s left wing, at a speed between 650 and 950 km/h, making a hole in the protective tiles made of reinforced carbon-carbon (RCC), close to the landing gear area.
During the re-entry into the atmosphere, plasma at 1500 °C penetrated through this hole in the left wing protective shield, and progressively destroyed the inner part of the wing. The crew lost the control of the shuttle. A few second later, the vehicle disintegrated.