One of the new features of the Windows 10 Creators Update was the ability to arrange your tiles into folders on Start (called live folders)
How to create a live folder:
A live folder can be created by dragging a tile onto another tile, Windows will then create a live folder. After you've created a live folder, you can drag other tiles into it and even change its size by right clicking it or holding on it and tapping the '...' button with touch.
