Basically, the entire layout has changed.
On your home page there is a messy mix of your feed and people's stories. Where stories used to be, there are random people and celebrities stories shown THAT YOU DON'T EVEN FOLLOW!
The update has rolled out for iOS only, so for now, Android users are safe.
Swiping left will now bring up a page of things that people have called "random junk" instead of the safe feed you have been accustomed to.
Users are demanding for the app to go back to how it was before, even creating a petition!
If you can't see the update on your phone, all you have to do is close the app completely and then re-open it. So if you want to savour the old Snapchat for as long as you can, don't exit the app!
Snapchat have yet to respond to the HUGE criticism on Twitter.