I'll cover the median versus the average. For those who aren't familiar with the median, that's the point where 50% of the population is making more than that, and 50% are making less. It's right in the middle of the distribution.
We've moved to that in income because we find a few very high values will throw off the average, so when we really want to compare we tend to look at medians. But there's still a difference between the average income between men and women as well.