Here's what I wrote up the last time I was asked this on OotL:

So, I was going to explain, then I realized I wanted to make sure I knew everything myself, and ended up writing this.

I would almost applaud avoiding it, but if you are interested, as neutral and to the point as possible:

• Zoe Quinn puts out a game/interactive fiction/visual narrative called Depression Quest

• There was a lot of critical praise for the game, especially for tackling the subject matter it did. There was also backlash to this, such as: it barely qualified as a game, the subject matter was handled poorly, the subject matter was the only reason the game got any attention.

• Some time later, Zoe Quinn's ex-boyfriend wrote a long blog post about how she cheated on him, and alleged she slept with several game reviewers/writers in return for positive press.

• While she had received various hate mail/threats/trolling before because of Depression Quest, doxxing of Zoe Quinn began in earnest after that blog post gained traction.

• Anita Sarkeesian, feminist, video game writer, and producer of a video series examining the role of women in the context of video games, who had already drawn ire for that and other reasons, both supported Quinn and was quickly embroiled in the conflict in her own right.

• Nathan Grayson, a writer for fairly prominent game blog Kotaku, owned by Gawker, is named as one of the people Zoe Quinn slept with for coverage.

• The editor in chief of Kotaku publishes a statement: That while the two were currently in a relationship, Nathan had only written one piece about Zoe Quinn, and it was unrelated to Depression Quest. (Whether or not this is true is the source of the subreddit name KotakuinAction)

Those are really the key notes of it. After that point, it spiraled outward, so anyone with an opinion on feminism, sexism, video games, and video games journalism felt the need to make it about their point.

The biggest arguments, which still continue:

• Ethics in Journalism. Supposedly what all of this is about. Developers, publishers, and reviewers in video games tend to have close relationships, given the fields they work in, and the events they attend. There is intense criticism of some of these, and people allege that there is coverage/reviews that are unethical due to the relationship involved. However, this complaint frequently bleeds over into criticism of the increasing presence feminist/critical coverage of video games.

• Feminism in games. Some people think video game culture has been unwelcoming to women, and others think that it has been openly misogynistic, both generally arguing that this isn't an acceptable state of affairs. The opposing view holds that the renewed focus on feminism in video games is unnecessary/forced political correctness/women trying to control men/social justice warriors trying to enforce their world view on everyone.

• Harrassment/Doxxing. This has been a problem for outspoken feminists before any of this happened. However, many people who spoke out on the side of Zoe Quinn, regardless of involvement in the industry, received death threats, and had private information such as their home address made public. Women who spoke out tended to be targeted more than men who made similar comments, though it was by no means only women doxxed. (An example of threats sent to Brianna Wu, feminist video game designer, GRAPHIC LANGUAGE)

Due to the anonymous nature of everywhere it was discussed, however, Gamergate continues to mean whatever the person talking about it feels like. On the same note, because of the anonymity, it can be overwhelmingly hostile and threatening without much recourse. It's a nebulous beast, with no leaders, and no mission statement, and thus, almost impossible to find a True Scotsman.