When you right-click an application when it's running you get the option to "Pin this program to the taskbar" so you can have a shortcut to normally what would be an application you run often. Sometimes you may have created the shortcut on the Desktop and then dragged the icon to the taskbar which would now store it there.
%AppData%\Microsoft\Internet Explorer\Quick Launch\User Pinned\TaskBar
Click on Run (or Search) and paste the line and press enter. All the shortcuts can be viewed and edited.