Gender constructivism, in short, is the idea that gender norms are socially constructed rather than being somehow essential–viz., there is no essential “maleness” or “femaleness”–which would be gender essentialism–that somehow transcends history and culture and–in the case of “maleness”–inhabits all humans who have penises from birth (which appears to me to be an even stranger idea now that I see it written down).
Often it is objected that these lines of thinking want to eradicate difference and make everyone–men and women–the same. However, in fact the opposite is the case. Constructivism wants to recognize that every single person is different, and that it is extremely problematic to try to reduce all of these differences to an either/or of male/female. Not surprisingly, trying to reduce difference to these socially conditioned gender roles can be emotionally and psychologically damaging insofar as one faces high levels of social pressure to conform to the gender role prescribed to her on the basis of her genitalia and made to feel ashamed when she fails to do so.
And anyway, if there were truly such things as essential “maleness” and “femaleness” these characteristics would have to be universal and exceptionless. As soon as there is one exception, essentialism no longer holds water as an adequate explanation of apparent gender differences. I know of no such exceptionless characteristic that has ever been specifically and determinately demonstrated. And any apparent universal trait is typically easy to explain as a result of social condition (i.e., “Boys tend to be more aggressive” is easily explained by the fact that, from the time that they are born, boys are both directly and indirectly receiving messages from parents, siblings, other children, teachers, preachers, TV shows, etc. about how boys are “supposed” to act and “not supposed” to act, and it is therefore not surprising when a young boy tends to develop these same characteristics. In other words, from a very young age, difference is suppressed and confined to one gender role or another rather than allowing the child’s individuality develop free from social pressure and the fear of being made to feel ashamed for not being “manly” enough, being too “girly”, etc.).
So, rather than seeking to eliminate difference, gender constructivism wants to free up difference, to loosen it from the either/or grip of gender essentialism, and to allow each individual to be an individual.