Understanding the types of sandboxes
As mentioned in an earlier section, we have some options when it comes to sandboxes. Sandboxes are separate Lightning Platform environments that can contain declarative configuration, programmatic code, and in some instances data that reflects the entities that are contained in the production org. Sandboxes are separate and isolated from the Salesforce production organization, so changes to settings, configurations, and code that are performed in a sandbox do not affect the Lightning Platform production environment, and vice versa.
To view and manage your existing sandboxes or create new ones on the Lightning Platform, you need to log into your production org, as this is where the option for maintaining sandboxes is located. Sandboxes are not available from within the Developer Edition, so if you do not have access to a licensed production edition, you will not be able to get to the sandbox setup screen.
Access to the sandbox setup screen...