What is the difference between copy and move in restoring database?

The Restore Database window states that:

This database might have been moved or copied.

In order to avoid conflicts between databases, Odoo needs to know if this database was moved or copied. If you don't know, answer "This database is a copy".

While it makes sense that there is a difference, it is not clear what exactly. In what case should one use copy and in what move?

Odoo version: 9.0c

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