Yes, a "tax refund" is the amount returned to you to reflect the amount of tax you overpaid. 

In the USA, the government (Internal Revenue Service = IRS) takes from your paycheck the amount it is estimated that you will owe.  The amount is based on the number of dependants, the amount of salary it is estimated you will earn during the year, etc.  (You have some control over this amount.)  This becomes very complicated when the pay is related to commissions as opposed to a stable monthly salary.  After all, you may do quite well one year and poorly the next.  Or  maybe this year is much better than last year.  If you receive an unexpected amount of money, you can send part of it to the IRS before the end of the year.  It gets complicated.  The laws are complex.  The Receita Federal  is simple in comparison. 

You do not want to owe money to the IRS.  You can be charged interest on it, be fined, etc.  Most unpleasant!