You will received an in-apps notification when a member:
- notify you in the comment
- notify you in the issue while creating an issue
- added you to a project
- assign a task to you
To check on the notifications you received in Backlog, click the notification icon on the global navigation and a notification summary will display.
You can go to the notification's designated Issue page by clicking the associated notification. If you are notified that you have been added to a Project, clicking the notification will bring you directly to the Project Home page.
The background indicates the status of the notification:
1 - Yellow: New
2 - Grey: Checked notification
3 -White: Unchecked notification
Besides that, you can filter your notification by user or by unread only.
Please check here for details about notifying a user.