This article shows you how to collaborate with other Salesforce users by mentioning them in Chatter Posts.

To mention a Salesforce user in a Chatter Post type "@" and start to type the users name. You'll see a dropdown list appear which contains users that you're able to reference.

After selecting the user/s and completing your post, the user will receive an email with details of your post and a link to the record in Salesforce.