A triplet is a set of three equally spaced spikes. The SETI@home screensaver tests for triplets by looking at every pair of spikes above a certain threshold power. It then looks for another spike precisely between the two spikes. If one is found, a triplet is logged and sent back to Berkeley.
The "power" tells us how strong the triplet is, relative to noise. The "period" tells us how far apart the three spikes are (in seconds).
For a more technical description of the SETI@home data analysis see the The SETI@home Sky Survey paper.
Copyright ©2001 SETI@home