GPWS = Ground proximity warning system; older systems use RADALT to provide the signal - combined with approach algorithms.
EGPWS = Ehanced GPWS has the addition of a forward looking function (a terrain database).
TAWS = Terrain Awareness Warning System has both altitude alerting and a forward looking function.
Later and cheaper (TAWS) systems can have all functions in a single box with GPS providing the position and geometric height information (it is not necessary to have a RADALT).
All regulations mandating these systems also have requirements for training.
Offshore helicopters in Europe also have a system for setting the height and voice alerts - Automatic Voice Alerting Device (AVAD).
It is likely that TAWS, with a forward looking function, will be recommended in any proposal to amend Annex 6 Part III.