The 'cello and bass use this sign most. It is a bass signature. However, pianists use both treble and bass signatures. When you see this sign you know the music you will hear, whatever instrument it is played on, will be in the lower register - deep.
Pianists develop their right hands more than their left, so often dread seeing the bass sign which signifies their weaker area of performance. If you get mixed up with the symptoms, remember the more fancy one is the treble clef. This one is the bass.