Did anyone answer this yet? If so, I apologize for repeating.
The Ledbetter act requires that if a group of people are doing the same job, the women have to be paid as much as the men. I don't know the exact wording or the regulatory or enforcement mechanism for compliance.
The origin is that Lily Ledbetter was doing the same job as several other people, all men, in her company. As is usual in corporate America with salaried employees, salaries are kept secret,and are set by individual agreements between the company and an individual employee. She didn't know that the men were making more than her. When she found out, she sued on the grounds of gender discrimination, but lost. The court ruled that it was not her gender that caused the discrepancy, it was simply that she had not negotiated for or demanded a higher salary.
This pattern is very common. Women in these sorts of roles tend to get paid less than men. The reasons could be very complicated, but I prefer a simpler explanation. They pay women lower salaries because they can. Companies will always pay employees as little as possible. The Ledbetter law does something, I'm not exactly sure what, to ensure that women are paid as much as men who are performing the same task at the same company.