Microsoft Teams is web-based productivity hub designed to help you with your daily productivity in one space.

Using mentions in Teams help you show information to specific people in your Team site. 

Please view the article from Microsoft on how to use the Mentions option to show information to specific people in your Team. 

Please Note:

• Use the @ function before a person's name.
• You do not always have to use the @ function. You can type a person's name as you normally would. Make sure you capitalize the first letter of their first name. 
• You can mention an entire Team and an entire Channel.