Answer
Real Accounting:
Dr - What comes in
Cr - What goes out
Examples of this kind of transaction include cash/bank and rent.
Personal Accounting:
Debit is the receiver.
Credit is the giver.
An example of this kind of transaction is Vendor/Customer relations.
Nominal Accounting:
All gains and income are credit.
All losses and expenses are debit.
An example of this kind of transaction is sales and/or purchases.