Wage Gap real or myth?

I've been told the wage gap is a myth from several different people. Ivanka Trump recently posted on her Facebook promoting equal pay, but people are getting angry with her & saying she's promoting a myth. I haven't done much research on it but I'd figure I would ask you ladies about this since y'all seem to give very helpful & educated answers most of the time on here! Is the wage gap real or is it a myth designed for politicial reasons? Give clear evidence & sources for your point of view!