I am newbie here,
I want to know if my computer reboot/sleep/break, do the program can resume task?
BOINC will restart after a reboot, if you told the installer to start Boinc with Windows startup.
BOINC doesn't like sleep/hibernate. It will try to write to disk quite regularly (multiple times a second), so before you let your Windows go to sleep/hibernate, make sure you exit BOINC.
You can always exit BOINC by hand (Boinc Manager, File->Exit) and then later restart it by hand (Start->Programs->BOINC->Shortcut to Boinc Manager).
I'm new to this ,but already have some credits. The question is what are the credits an what are they for?
Credits are a way for the project to pay you back for the work your computer is doing.
They cannot be used for anything (as of yet), other than to brag with and showing off how good your computer is.