can somone explain what iso bin cue and the rest

hi i'm asking what are bin iso cue you don't get any of that with psx but dreamcast you realy have to dream i brought my son a DC for chistmas and he's scraced 2 games now i go searching the web and you hear of bin etc etc
what are they all and how can i back up the other 4 games cause i can't afford to replace the other ones

Thanks To Anyone That Can Help