Dialog windows and flash notifications are used to notify you about something important.
If just a notification is needed (e.g., to mark the success or failure of an operation, a reminder, etc.), the flash message will appear.
If your decision is required, and your Oro application cannot proceed without it, a dialog window will appear and will remain in place until you click a button. They usually pop up in order to warn you about something very important or irreversible, such as deleting records.
The dialog windows have buttons and will not disappear until a decision has been made: