Each production org has a limited number of sandboxes available to it, that can be used for development and testing.

Sandboxes are available in different types, which determine the environments capacity and how often it can be refreshed. When a sandbox is refreshed, a new copy of the production org is created to replace the current sandbox instance.

Refresh time is variable, and the process can take minutes, hours, or days, depending on the size of your org and available bandwidth on the platform. (Salesforce Partner Support cannot prioritize or rush a refresh; it takes what it takes.)

Each sandbox instance is given its own Org ID, even when it is a refreshed sandbox, but every sandbox uses the same record IDs and record type IDs as the production org.

The number and type of available sandboxes depends on the Org Edition and whether additional sandboxes have been purchased.

For more, see Sandbox Environments in Salesforce Help & Training.