BOINC? What is that?
The BOINC client doesn't crunch anything. It is a managing program, with which you can attach to scientific projects to download their applications and work.
It consists of 3 major parts: - the Boinc daemon. This is the actual program that runs in the background. - the Boinc Manager. This is the Graphical User Interface with which you can control the daemon. - the Boinc screen saver. This shows the screen saver of the science application, if there is one built in in the science project's application. If not, it shows the standard Boinc screen saver.
The science applications of the various projects do the actual 'crunching'.
If you want to see Dr. David Anderson explain it to you, please follow this link to YouTube.