Oops, too much champagne already...
Well, I'll try again:
Normally the aircraft will receive taxi instruction to the runway in use holding point via a specific taxi route (no hold short instruction necessary, unless the taxi route will cross another runway at which ATC might require a "hold short runway xx" instruction). The clearance limit in this case is the runway holding point at the CAT I holding point (only CAT II/III when so instructed most likely during Low Vis conditions).
Other times ATC will instruct an aircraft to hold short of a taxiway or taxiway-intersection due to traffic, or awaiting parking, or just because they can....
Back to the champagne....