Form 16A is also a TDS Certificate for TDS deducted on Income other than Salary. While Form 16 is for only salary income.
For example – a Form 16A shall be issued to you when a bank deducts TDS on your interest income from fixed deposits, insurance commission, rent receipts, etc.
Form 16A has details of the name and address of deductor/deductee, PAN/TAN details, challan details of TDS deposited. It also contains details of income you earned and the TDS deducted and deposited on such income.