YouTube has introduced a new Trending tab, that appears on the website and in the mobile apps next to your Subscriptions tab. The tab had previously appeared for some users on a trial basis but it's now permanently included.
The Trending tab shows videos that are, well, currently Trending on YouTube. The tab shows international as well as regional trends, so you will see a lot of popular local videos along with international favorites.
Unfortunately, people aren't taking too kindly to this feature as in the app you now have to swipe twice to go to your subscriptions, which was previously just one swipe away, but your mileage may vary. It's not something that can be disabled, though, so you're stuck with it whether you like it or not.