The copy command as the name implies, is used to make a copy of an entity. 

To copy an entity, do one of the following: 
 
Choose Copy from the Modify drop down menu (do not choose the CopyToClipboard option)
On the Modify toolbar, click the Copy tool. 
Type COPY in the command line and then press Enter.  
Select the entity right click and select Copy.
 
Tips
Use copy together with Tracking. Set additional tracking angles as required.
The ROTATE command can be used to generate a circular array. Hold the SHIFT key down while copying around a center point.

Copy