Gender bias is when a company doesn't decide by anything relevant to the job (such as skills, quality or work discipline), but instead decided mostly by the sex. And this is happening. Female programmers are getting hired even when their skills/productivity/experience is way lower than male programmers.
I don't want to get into the whole "positive discrimination" debate and my own thoughts on the matter are complex and change frequently.
However - the arguments for, against and for many points in between have been stated many times. Either you already are aware of them in which case you should be engaging with those rather than restating a starting position - or you can just do a Google search and get up to date with what is a fairly complex and nuanced topic.
