To begin with, Twitch will replace the Pulse social component on the homepage with more recommended streams based on your viewing habits (you can see a preview below). It's simultaneously reworking channel pages to help you find videos and the buttons for following and subscribing. In the long term, Twitch is promising more game-specific filters to help streamers categorize their broadcasts based on what's happening (such as the choice of character), improved recommendations for smaller channels, better search and tags to help describe streams.
Both the roadmap and the changes themselves have one clear goal: help small-time streamers. While many associate Twitch with big-time streamers who can pull in tens or hundreds of thousands of simultaneous viewers, there are many small-scale broadcasters who may see a huge impact on viewership with even modest changes to the experience. The outline helps them prepare for those changes and, ideally, become as popular as their idols.