Your Presence Status and Location are settings you can configure in Lync to tell other people whether you are available, and where they can find you. Additionally, it's possible to "tag" a contact so that you are alerted whenever they become available. Finally, a custom message can be created to provide further information to people on your current situation.
Mac Users: Although the Mac version and Windows version of Lync have different appearances, the processes for changing status, location, and the custom message are very similar. Therefore, there are no separate instructions for Mac users. Any significant differences between the two versions will be made obvious. For example, it is not possible to set a "location" in the Mac version of Lync.