Mac storage basics · Library folders explained
What is the Group Containers folder, and can I delete things in it?
Short answer: It holds data shared between apps from the same developer, often their real data. Leave folders for apps you still use; leftovers from apps you've removed for good can be deleted.
Group Containers (inside your Library) holds data that several apps from the same developer share — for example a suite of office apps, or an app and its widget. It's often where a messaging or office app keeps its real data.
Don't delete folders here for apps you still use: you can lose messages, settings or offline documents. If an app is gone for good, its leftover group folder can go — the folder names usually contain the developer's name, so check before removing anything, and use the app's own settings first when it offers a way to clear its data.