In May and in mid-October, the orbit of Halley´s Comet is extraordinary close to the Earth. Then the small conglomerates of ice and dust the comet leaves behind collide with the Earth.
The meteor shower that appears in May is called Eta Aquarids, the October-shower is called Orionids, as the meteors appear to come from Orion the Hunter. These Orionids move at a speed of 147,300 mph.
The peak is today, on Oct. 21st.
Halley´s Comet passes near Earth only once in 76 years (next time in 2061).