@Pinging is a method for mentioning specific people to take the idea to their attention. Pinging is for addressing people who haven't previously noticed the idea but that you think should be aware of its existence.
To @ping someone, the user must have logged onto the board at least once. Pinging happens in the Discussion section of an idea.
Tutorial
In this tutorial, we’ll show you how to get a specific user’s attention regarding an idea. Let’s begin by opening an idea on any board.
We can either just directly ping a person to get their attention or add a comment along with the @ping to inform them of why their attention is required on this specific idea. When you write “@” into the text field, you will automatically get suggestions on who it is you wish to address. You can narrow down the number of suggestions by typing the person’s name as such: “@firstname lastname.” Usually, a few letters of the first name are enough to find the person you’re looking for.
After you find the person you’re looking for, you can click the blue “Send” button. This will publish your comment and automatically send a notification email to the pinged user, informing them of the idea they were mentioned in. The notification email will also include the message that is written along with the ping.
P.S. If you comment on someone’s idea, they will automatically get informed of the activity on their idea. The same applies to comments; the user will always get notified if their comment receives a reply. It's thus not necessary to ping the user in these cases.