The notifications tab is a page you can use to keep updated with everything going on in your JAI workspace, from changes to contacts to new engagements and updates to opportunities progression. The notification tab is identifiable by the bell on the main taskbar.
A small blue dot will appear on the bell if there are new notifications for you.
Notifications are slightly different from every other icon on the taskbar. Notifications do not have its own page, rather when you click on notifications, a side column on the right-hand-side will open on top of your current page. This allows you to look at notifications and get back to your previous task immediately.
By default, you will see all new notifications by order of most recent. But you can use the action and filter options to refine what you see or remove old ones.