Reg D sets forth requirements for how banks must manage its reserve requirements with Fed. Of particular interest in the Reg are the definitions of the various types of accounts (DDA vs savings vs time). The details of these account definitions help us understand account transaction limitations (such as MMDA limits) and what types of customers can maintain NOW accounts.
Reg DD is the implementing regulation of the Truth in Savings Act and sets forth requirements for disclosing account terms to our consumer customers, advertising, calculating interest/APYs, etc.
If you will look in BOL's Alphabet Soup link or "Click to Read a Reg" link you can read a brief overview of the Regs or pull them up to review the Reg sections in detail.
_________________________
Life without Jesus is like an unsharpened pencil - it has no point.