Credits are awarded for completing "tasks", and having them validated. Each Work Unit is sent out to, initially, two randomly selected users as tasks; when they have finished their tasks the two results are compared and credits are awarded, provided the task has not finished in an error (in which case you get no credit).
They have no monetary value, but are intended to be used in comparing the performance of our computers, both against ourselves and with other users.
Member of Seti PIPPS (Pluto is a Planet Protest Society)
Somewhere in the (un)known Universe?