Hover the mouse over some items and a pop-up will appear giving a brief description of what the control does or what input it needs.

 

Below is an image of the Tool Tip for the Add New icon on the Toolbar.

 

Below is an image of the Tool Tip for the Save Data icon on the Toolbar.

 

Tool Tips not only apply to icons (although that is the most common use) they can also apply to any other object.

Below is an image of the Tool Tip for the Sex field in the Personal Information section of the Data Entry window..