Profile Page - Notifications
Anytime somebody mentions you in the website, comments on one of your uploads, or if there's activity on something you're following such as a forum, you'll receive a notification.
If you have unread notifications, you'll see a little circle over the bell:
You can see a quick overview of your most recent notifications via the bell icon in the main menu.
To see all your notifications, click 'View notifications' at the bottom of the little screen that pops up when you click / tap on the bell icon.