Message Inbox:
In the main messages page you will see your inbox, any messages from members private or public will be visible in your list of messages.
You can reply to messages, and also create messages.
Message from member header:When you look at any members profile you can send them a message from clicking on the message buttons in their header area of their profile. See image..
Public Message:
A public message is like a public post. All members will see your message in the activity list. You can also post a message into a group.
