A notification is something that draws someone's attention to let them know that something has happened. Notifications exist in the real world as well as in the digital world. Without notifications the user would have to keep checking to see if something has happened, and since most probably nothing has, the whole exercise becomes a waste of time.

By relying on something to let the user know about an event, the user is free to work on other things. Notifications must be easy to recognize and must be distinguishable from other notifications. However, it is important that notifications don't become a distraction. Too many notifications can become a hindrance to productivity. If the notification is overpowering, the user will be forced to stop what they are doing.

In contrast, some notifications cannot be ignored and require a user's immediate attention and action. These types of notifications are very annoying as they usually appear at the worst of times, but they are also very critical. Sometimes a decision has to be made, and there is no avoiding it.

One of the features of a good notification is that it lets the user know that something has happened but does so in a subtle way. The user is aware of it but can choose to ignore it.