The Large Hadron Collider beauty experiment (LHCb) is a dedicated B
physics experiment at the LHC. The trigger system is of crucial
importance to discriminate the interesting B decays against the dominant
background from inelastic pp-scattering. The LHCb trigger is a two level
system. The first level is implemented in hardware. It reduces the rate
from 12 MHz visible collisions in the detector to a rate of 1 MHz. At
this rate, the full detector is read out. The second trigger level is a
software application running on an Event Filter Farm composed of 1000 -
2000 CPU nodes. First the hardware decision is confirmed using partial
event reconstruction. Events which pass this confirmation are then fully
reconstructed and the complete analysis of interesting B decays is
performed. With a rate of 2 kHz, data is saved to mass storage. In this
talk, an overview of the LHCb trigger system will be given. We put a
special emphasis on the software trigger level.