Figure 2.7 - Copies in the X-axis
Using the SHIFT+D keys gives you a lot of freedom to create all kinds of
copies based on the type of selection you have in Blender. For instance,
you can start making multiple copies from a selection of various objects
at the same time.
There is also another option for duplicating objects called Linked
Duplicate. By making a linked copy, you make an instance of your
selected object. Any changes applied to one object propagates to all
copies. Use the ALT+D to create a linked copy.
To unlink any duplicates created with the ALT+D, use the Object →
Relations → Make Single User → Object & Data menu. Select the
copied object and use that menu option.
Info: For some operations, you might want to create a copy of an object
that is in the same location as your original selection. By pressing the
ESC key after SHIFT+D, you create the duplicate but cancel the move