iPhone app- What does the phone icon do on a coworkers name?

 When logged into your app and looking at the roster for the day, you can select a coworkers name and 4 different contact method icons will appear.

The first of these icons is a telephone. If your co-worker has a phone number on their account, you can call them directly simply by selecting this icon.

They will be called from your phone as soon as the icon is selected.