SAP CRM Question:

It depends on the Landscape of your environment
Example: Sandbox – Development – Testing or Quality -
Production

In support process usually you replicate the issue that the
user has got in the testing or quality environment and then
try for a solution.

In Implementation, sandbox is used as a rough book to try
implementing and doing experiments, later you do a clean
configuration in Development and then transport the same to
Testing or Quality and finally go live to the production
environment.

Note: The above mentioned is just an example, the landscape
and process can be different from organization to
organization.