Form 16 is the TDS certificate for salary your employer issues; Form 16A is the TDS certificate for non-salary payments (interest, rent, professional fees).
Issued by banks/payers for TDS on interest, rent, commission, professional fees etc., every quarter. The figures also appear in your Form 26AS.
These are your proof of tax already paid. File using Part B of Form 16 plus your 26AS/AIS — and keep the certificates in case of a query.