Categories can be used to group different shortcuts together into separate tabs inside the app. Each category has a name and can contain zero or more shortcuts. You can switch between categories while on the app's main screen by swiping horizontally or by selecting the tab at the top of the screen below the title bar.
You can access the categories editor by clicking the left-most icon (three vertical bars) at the while on the app's main screen.
A category's layout type defines how shortcuts within it are displayed. There are currently only 2 options: list, which will display the shortcuts vertically below each other in a list, and grid, which displays them in a grid, similar to Android's home screen.
You can change a category's background to either be black, white, or to display your home screen wallpaper.
A category can be set to be hidden. A hidden category will not show up as a tab in the app. This can be useful if you have shortcuts that you only want to access directly from the home screen (make sure to place them first before hiding the category) or that you only want to trigger from other shortcuts, using Scripting or via a Multi-Shortcut.