OS X displays running programs slightly different than Windows. There are two main ways a program will show it is running: either in the dock or in the menu bar.
The picture below shows two programs (Google Chrome and Skype) that are closed and open, respectively, in the dock. You can tell Skype is open because it has a small gem under the icon. Chrome is closed and is only acting as a shortcut in the Dock. To close Skype, or any other open program, right click (or two-finger click) on the icon, and then select Quit. This will stop the application from running.
Another way a program will indicate it is running is by being displayed in the menu bar at the top of your screen. The image below shows Skype is active by being displayed in the menu bar. With a system that barely meets our System Recommendations, having a program such as Skype open could limit the quality of your Digital Clinical Experience.
The picture below shows a minimum amount of icons in the menu bar. If there are additional icons it could indicate a third party program is open.