Between Jupiter and Saturn. Between Uranus and Neptune. Between Mars and Jupiter. The largest asteroid is Ceres, which is about 1000km in diameter. Asteroids are thought to be the leftover planetesimals of the inner solar system that never formed a planet.
Asteroids are generally rocky in composition ranging from carbonaceous to silicate to metallic.
Most asteroids are in very circular orbits but tilted at an angle of almost 90 to the ecliptic. M-type asteroids are mostly iron and nickel. S-type asteroids are mostly rocky silicate materials. The asteroid Vesta is a large M-type asteroid located between Jupiter and Saturn. None of the above, there is no asteroid called Vesta.