Muting a member prevents them from posting threads, comments and sending messages. They'll see a message where the text input is telling them that they're muted. 
 

Muting Members as a Moderator or Administrator

To mute a member, go Settings > Members > Manage Members and select the member profile you want to mute. Here, click on the caret icon (⌄) and press "Mute".



You can also press the 3-dot menu to select this option when you are in the Manage Members list.

When you mute a member, you can also set a window for them to be unmuted: