Use the Copy command to duplicate drawing entities and place a copy of them at a specified location.
The duplicated entities are exact copies of the specified entities including all entity properties such as Layers, LineColors, LineStyles, and LineWeights, as well as the outline of the entities. Optionally, you can force the copied entities onto the active layer.
Based on one selection, you can create multiple copies.
In addition, you can create a specified number of copies in a linear pattern. See Copying Entities in a Linear Pattern.
To copy drawing entities:
This option exits the command after you specify the displacement.
Then specify a source base point for the copy.
Then specify a source base point for the copy.
If you press Enter, the source base point is interpreted as a relative X,Y,Z displacement.
The copies are placed at the specified positions. If the result of a multiple copy is unexpected, specify the Undo option.
To finish duplicating entities, press Enter.

You specify a base point (P1 in the diagram) and a destination point (P2) to indicate the distance and direction of the copied entities from the original entity. These points do not have to be selected on the original entity.
The Pattern command is an effective tool to create multiple copies in a linear or circular pattern.
The CopyNested command lets you duplicate drawing entities that are contained in a Block or a Reference
Use the Clipboard to Copy and Paste entities to another drawing. See Using the Clipboard.
Access
Command: Copy
Menu: Modify > Copy
Tool Palettes: Modify > Copy
Ribbon: Home > Modify > (Flyout) Copy