I’m assuming DDA stands for demand/direct deposit account. Keeping a separate one with a low balance for internet accounts can help keep a primary account unaffected if paypal or other internet services initiate a transfer without your permission (could also be due to a compromised paypal account).
Thank you!
Direct Deposit Account ?
Demand deposit account.
This is the technically correct term used with US-based vanilla bank accounts that are FDIC insured