I am little bit embarasst to ask this question.
I don’t understand whole thing called tax return,why should I get tax back?
When I buy something and pay let’s say 10% do I get money back or whatever?
I could never comprehend this stuff.Explain someone please this to me ,but in fairly simple language. 
Tax returns apply to income taxes, not sales taxes. When you receive your paycheck, your employer witholds a certain percentage and sends it to the government (people who are self-employed have to send tax payments to the government themselves). At the end of the year, for a variety of reasons, many people find they have overpaid. They file a tax return in order to get their overpayment back.
You can tell your employer to reduce your tax witholding if you prefer not to overpay over the course of the year.
For the record, doing this may also require you to owe taxes to the government at the end of the year too.
One point of wording:
The form you fill out is the return. The money you can get, assuming you’ve paid too much tax over the year, is the refund.
This is, understandably, a bit confusing. The form is called a return because you’re returning it, filled out, to the government.
Depends how the taxing authority has structured the taxes. A tax return can be tied to sales taxes, depending on the jurisdiction.
For example, in Canada the federal government levies a federal income tax and a federal sales tax, called the Goods & Services Tax. One of the policy concerns about sales taxes is that they are regressive - low income people tend to pay a larger proportion of their income in sales taxes than do people at the higher income levels. To respond to this concern, the federal government offers a rebate on the GST for people under a certain income level, which they can claim on their income tax return.
I’m aware that the U.S. government doesn’t have a sales tax, but I understand that some states do. Do any states offer a similar rebate? If so, they might use the state income tax returns to decide who is eligible for the rebate.
It’s my understanding that anyone with income has to file the return, not just those that have a refund owing. If they owe more than has been deducted during the year, the tax authorities will obviously want to know about it.