The Explore Tab will recommend different topics, channels, or videos that wouldn't typically come up in a user's traditional feed. Explore Tab recommendations are still personalized and are based on viewing habits, but it's essentially a greater range of content.
YouTube Director of Product Management Tom Leung explained the concept in the video announcing the feature.
The idea behind Explore is for viewers who say 'Hey, you know I like all these recommendations based on what I view, but sometimes it's like too much of the similar stuff' and they want to kind of broaden their horizons a bit. Explore is designed to help people be exposed to different kinds of topics, videos, or channels that you might not otherwise encounter.The Explore Tab is in testing and it is available to one percent of iPhone users who use the YouTube iOS app. Users who are selected for testing will see a new "Explore" tab at the bottom of the app alongside the "Home" tab, a Subscriptions tab, a new Activity tab, and a Library tab.
While the Explore Tab is limited to a small number of users at this time, if it is successful, YouTube plans to roll it out to a wider number of users.