Twitter has been making some nifty little changes to their app as of late, with things like the "while you were away" feature and the attempt to give you an easier sign up process by scanning your contacts when setting up Twitter for the first time, so that they can provide users with a recommended set of people to follow based off people you know. There is a new feature that it looks like Twitter is close to rolling out to the app which would allow users to view links within the application. It's basically a built in browser so tapping links will no longer have to navigate the user outside to either the stock browser, Chrome, or whatever other browser that may be installed.
Think of this as similar to the way Facebook's app is now set up. When users scroll through their Facebook feed and tap on a link, those links open up in a new built-in browser page within the Facebook app itself so you don't have to leave Facebook, although an option is given to open up those pages in an actual browser if users choose to do so. It appears Twitter is looking to implement the same feature, and is just one of the many new things they're doing to give the app and service some new life and keep users engaged.
Seeing as how this is a feature that some users already have a hold of but there has been no new update, this is a feature that Twitter will have to likely turn on from their end, which means it could show up soon and it could still be weeks away if they're currently testing. When and if Twitter actually rolls this out to all of its app users is unknown, although this is a good candidate to be a likely well received feature within the app. Not only does it keep users in the Twitter app by cutting out the need to exit to a browser(which happens automatically of course), but it makes it easier for users to get right back to scrolling through their timeline should they want to continue browsing tweets.