'Xrefs’ is used in AutoCAD to

Explanation:

Xrefs: Attaching and Detaching Referenced Drawings 

• You can attach any drawing file as an external reference or Xref in the current drawing.
• Attached Xrefs are links to the model space of a specified drawing file.
• Changes made to the referenced drawing are automatically reflected in the current drawing when it's opened or if the Xref is reloaded.
• The attached Xrefs do not significantly increase the size of your current drawing.

By using referenced drawings, one can

• Coordinate your work with the work of others by referencing other drawings in your drawing to keep up with the changes being made by other designers. You can also assemble a master drawing from component drawings that will change as a project develops.
• Ensure that the most recent version of the referenced drawing is displayed. When you open your drawing, each referenced drawing is automatically reloaded, so it reflects the latest state of the referenced drawing file.
• Keep the names of layers, dimensioning styles, text styles, and other named elements in your drawing separate from those in referenced drawings.
• Merge (bind) attached referenced drawings permanently with your current drawing when the project is complete and ready to be archived.

Important Points

An external reference can be a drawing file, image, PDF, or one of several other file types.

An Xref is an external reference that's specifically a DWG file.