few questions regarding csc

cleaned the resgistry, disk and privacy with csc with all the default settings. everythings fine. but few questions –

  1. under disk cleaner-cleanup- windows update temp files is not checked by default. is it safe to clean it??
  2. under privacy cleaner-application-internet explorer- what are backups and streams?? please give little info on these
    two. is it safe to clean both??
  3. under privacy cleaner-windows-what are system backup files, printers spool files, driver cache, dll cache, reg edit
    favourites list, chkdsk fragments, registry streams mru, open locations and install locations?? all these are checked
    by default. is it safe to delete all these?? if possible little info will be good.