Overtime is the wages you are owed for working beyond the minimum required per work week. Under federal law, nonexempt employees must receive overtime pay for hours worked over 40 per workweek at a rate not less than one and one-half times the regular rate of pay.
Keep in mind that federal law does not set a limit to the number of hours you may be required to work during your workweek (with the exception of employees 15 years or younger). Accordingly, your employer may require that you work 50, 60, 80 hours or more during your work week. Of course, if you are not exempt from overtime, you must be paid for hours worked over 40 during the week.
Likewise, the law does not require that you be paid extra for working on weekends or holidays, so long as that time does not take you over the 40 hour limit.
Limit this discussion to the definition of overtime. All other discussions should be located on the FLSA page.