These are general settings for the realm.
Whether the realm is active or not. Marking a realm as inactive disables all authentication and other activity for the realm, but keeps the data and can be reactivated at any time.
Mostly used in the UI, but can also be used as a merge field in outbound emails. For production realms, we recommend something like “My App”, whereas for dev, testing, etc., we suggest adding a qualifier like “My App (staging)”. The title of your hosted login pages is set elsewhere, so this doesn’t necessarily have to match that.
Reference is an optional ID that you can use to map a given realm to a corresponding resource in your app. For realms, it is mostly only useful if you are creating realms via the API (perhaps in conjunction with a multi-tenant app where each tenant gets their own realm). This field is searchable via the API.
Delete realm is also in the lower right, for users with “Manage all realms” permissions. Deleting a realm deletes all data and event history immediately.