CCS, NCCS, DCCS, SHAC, AAD – What does it all mean?

In Scouting various abbreviations are used and these are just a few.

CCS – Catholic Committee on Scouting
NCCS – National Catholic Committee on Scouting
DCCS – Diocesan Catholic Committee on Scouting
SHAC – Sam Houston Area Council
AAD – Ad Altare Dei