The To the foreground 
button [Editor -> Tools] brings the selected entity 'to the foreground' against other entities. This will make the entity fully visible - without any other entities overlapping it. The To the background 
button allows to move the selected entity to the background level against other entities of the drawing. Thus, some other entities may overlap it. In the classical menu the commands can be found under the Tools menu [Tools -> Display Order].
The display order of the selected entities after using these commands depends on the order of their selection. The first selecte4d object will be displayed in the background relative to the other selected objects. For example,
Note: The objects are selected from the image with the initial position of colored circles.