Meteoroids are the debris sloughed off from comets. When they reach the Earth's atmosphere and burn up, they are referred to as meteors; otherwise known as shooting stars. Those that hold together and actually reach the Earth's surface are known as meteorites.
It was once calculated that the Comet Swift-Tuttle was on a collision course with Earth, suggesting that an impact was likely to occur in the year 2026. That theory was quickly debunked as recalculations of the nearly dual century data showed differently. The new theory is that in the year 3044, the Comet Swift-Tuttle will brush by within a million miles of the Earth, considering this future event to be a true 'cosmic near miss' by astronomers.