Earth is going to pass through the debris of comet Halley during its orbit around the Sun. This debris will be seen as meteor when they enter into our atmosphere. The peak of the shower will be between 21-22 nd October,2011. There will be moon in the sky but it is expected that one may see 20 meteors per hour from place free of light and other pollution. It will be seen after Midnight and before dawn.
For more information about Halley's Comet see: Halley's Comet
The name Orionid is given because meteors can be seen coming from the constellation orion.
There are many good articles about this shower: Please have a look at it
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Have a good observation