Form-16 is a certificate that your employer gives you as an acknowledgement of the deduction and deposition of the total TDS (tax) deducted from salary with the Income Tax Department.
Details of TDS deducted and the details of salary, allowances (like amount paid for housing rent, medical reimbursements etc) & deductions are mentioned in Form-16 (Part B).
It is given after the end of year and helps you file your income tax return.
Form 16 might differ in formats depending upon employer to employer but a standard form 16 looks like this :-
Part A of FORM 16 contains details of tax which is deducted from your income by the employer while Part B gives the detailed breakup / composition of your income details and dedcutions etc
Read More Form-16 Everything you Need to Know.