It started when a woman called Zoe Quinn and her partner split up. Ms Quinn was a game developer and her ex wrote a blog where he stated that she had slept with a gaming journalist, who's name escapes me, in order for him to write a favourable review of a game she was involved in. Slight problem, Ms Quinn admits she slept with the guy, however, he had had no input into any review of any of her games and the ex knew this, but wanted to discredit her, he admits this, but says that what he did was fine because.... Insert stupid reason here.
The problem is that this lead a bunch of men, who had already been harassing women game developers, to have a CRUSADE against evil women fucking journalists for reviews.
Anita Sarkeesian had run a crowd fund to do a series of Vlogs about how hideously sexist the gaming industry is, and the gamergate loons then went for her too. There are some major players, thunderfoot being one, who, while offering nothing to refute great swathes of AS's work, picks on tiny things she gets slightly out of whack and posts long rants about it on YouTube.
The more serious ones, and one of the big boys is ex US military who makes no bones about calling in Intel favours, have a chat channel associated with 8chan where they plan Twitter hate campaigns, share personal info (addresses, social security number, phone numbers etc, etc, etc) with each other so that they can better threaten these women.
They have not only threatened, they have destroyed Ms Quinn's career. They post bomb threats, rape threats, personal info on Twitter and Facebook. They pretend they aren't misogynistic, and attack anyone who says they are. They are closely linked with some really nasty people in the MRM as well.
The latest one I've heard of is AS having to cancel a talk in Utah, because a man posted online, sent emails etc that he was going to do a school shooting like no one had ever seen and the Utah police refused to stop people concealed carrying.....