Bed Bugs are tiny parasitic insects that feed on human blood. They are primarily nocturnal and tend to hide out during the day. Their tiny eggs are usually laid in fabric seams or fibers.
Bed bugs find hosts by detecting either heat or trace chemicals (such as carbon-dioxide) emitted by live bodies. They typically prefer a stationary host who is asleep but if hungry will take what they can get. You can even be bitten while awake sitting in a chair.