A Sandbox is a personal environment where you can experiment with Brightspace. You have access to all necessary functionalities, and can try them out without possible unwanted consequences for yourself or your students. The Sandbox is private: only you and the colleagues you have enrolled can view its content.
The Sandbox is a useful tool that will help you get used to Brightspace. You can, for example, experiment with new ways to present your content, create new tests for students and discover ways to improve interaction with students. You can also prepare a course in your Sandbox and export it to a public course when satisfied.
Take note: the Sandbox is located in the production environment of Brightspace. Normally only you have access to the Sandbox. You can however add other existing users if you want. Only add someone if said person has consented. Keep in mind that the enrolled person can view everything in your Sandbox, when he or she has the same role.