Valve is adding a new filter on Steam. The aim is to provide users with the means to avoid certain kinds of content. The Adults Only filter is meant for games that feature "explicit sexual content". The other new filter is called Mature Content. Mature Content is for games that deal with mature subjects, but don't contain sex or violence. Previously Steam had filters for Frequent Violence/Gore and Nudity/Sexual Content.
This, of course, means that games falling under these filters can now be found more easily on Steam. Valve has also added the ability for users to ignore games from specific "developers, publishers, and curators".
Thanks, Games Industry.