Short answers, pulled from the story.
The asteroid belt is a torus-shaped region of the Solar System centered on the Sun, roughly spanning the space between the orbits of Mars and Jupiter. It contains millions of solid, irregularly shaped bodies called asteroids or minor planets, with the average distance between them about one million kilometers.
Giuseppe Piazzi, chairman of astronomy at the University of Palermo, Sicily, discovered the first asteroid on the 1st of January, 1801. He named it Ceres, after the Roman goddess of the harvest and patron of Sicily.
Jupiter's gravitational resonances pumped excess energy into the region, driving collision velocities too high for planetesimals to accrete into a planet. As Jupiter migrated inward, these resonances swept across the belt, ejecting most of its original mass; less than 0.1% of the original material remains today.
The three primary types are C-type carbonaceous asteroids, which make up over 75% of visible asteroids and dominate the outer belt; S-type silicate-rich asteroids, which are more common in the inner belt within 2.5 AU of the Sun and comprise about 17% of the population; and M-type metal-rich asteroids, which are found mainly in the middle belt and whose spectra resemble iron-nickel.
Kirkwood gaps are empty zones in the asteroid belt first identified by Daniel Kirkwood in 1866. They occur at orbital distances where an asteroid's year is a simple fraction of Jupiter's year, causing Jupiter's gravity to repeatedly nudge asteroids out of those orbits and into different trajectories.
On the 22nd of January, 2014, European Space Agency scientists using the Herschel Space Observatory detected water vapor on Ceres for the first definitive time. Main-belt comets beyond the belt's snow line, at 2.7 AU from the Sun, have also been proposed as a possible source of water for Earth's oceans.