Container widget allows you to better organize your app's space. It's a blank section in which you can place all of the other widgets. A useful trait of this section is that you can 'hide' it on the app preview/ instance - you can make it collapsed or expanded by clicking on the arrow.
Options of this section:
Caption - which can be both just given or computed by a formula
Initially collapsing - which can be set to be done automatically by clicking the 'initially collapsed' option
Hide header - you can choose if you want to hide header of container
Alignment - you can choose to what align the items in the container (Left, Center, Right)