First, it must decouple the record from vibration entering it via the turntable, this includes bearing noise, transmitted motor noise through the drive system, cartridge feedback, chatter transmitted via the tonearm into the turntable, ground and air-borne audio feedback, underground pumps, etc.
Second, it must absorb and transmit resonance out of the record itself. A stylus vibrating in a record groove sets the vinyl resonating in a way that will feedback into the stylus if not highly controlled. This may be momentary to the tiniest fraction of a second, but will nonetheless create a blurring of the signal and overlay other parts so that they will not be heard. In other words, there can be loss of information and addition of spurious noise to the intended signal.
Third, it must transmit the drive to the record without elasticity or slip. The surface that the record sits on in response to the amount of drag on the record. At best, this will be a very slight momentary elastic movement backwards, but enough to slightly deaden the impact of a bass note drum strike. At worst it will cause the record to slip backwards, which is only obvious when you can hear wow occurring–as in the case of a badly dished record that only contacts the platter in the centre.