Twitter can't really figure out what it needs to do to drive user growth and activity but not due to a lack of trying. The microblogging platform wasn't afraid to experiment with a whole bunch of different features in recent years. Most of these new features which were either tested or fully integrated into the service were aimed at incentivizing users to actually interact with both the platform and other users. Namely, Twitter's biggest problem that's been plaguing the company for quite a while now was not getting more users, not even getting more visitors, but getting existing users to actually log in and do some tweeting of their own. Sure, the user growth numbers could be a bit better but it's the user activity—well, lack of—that's hurting the company the most. Twitter currently has over 600 million unique visitors each month and more than 300 million of registered accounts but "only" about 100 million of users are active on a monthly basis.
Given how a social network whose users aren't exactly sociable is bad news for both advertisers and shareholders, Twitter is doing whatever it can to change things. It's testing features at a rapid pace and hoping that something sticks. The latest such feature is called Explore and it's designed to make the microblogging platform focus on content discovery. The idea makes perfect sense - if you can get users to see more content they deem interesting, there's a better chance they'll be willing to interact with the same content, i.e. the source which posted it. The Explore tab doesn't seem to be tested as a Twitter Moments replacement, but rather an alternative.
The new feature is currently being rolled out to users worldwide though the company notes that this is still just an experiment. In other words, not everyone will see the Explore tab today, some may not even see it by the end of the week and a significant portion of users probably won't see it at all unless the experiment proves to be a success and Twitter decides to officially integrate the Explore tab. There's still no info on how long this testing phase expected to last but Twitter will presumably have more news for us soon.