The bill, S. 84 [sic] seeks to amend the Fair Labor Standards Act of 1938 and require employers to prove that differences in wage are the result of differences in merit, not gender. It also prohibits retaliation against employees who file claims of wage discrimination, and allows victims of wage discrimination to seek punitive damages for lost wages.
It seems like the primary purpose of the bill is to close a loophole in the Equal Pay Act of 1963 that allows employers to pay employees differently on the basis of “(1) a seniority system; (2) a merit system; (3) a system which measures earnings by quantity or quality of production; or (4) a differential based on any other factor other than sex”.
(4) is the loophole; you can shoehorn a lot of sexism into criteria that aren’t, strictly speaking, “sex”.