Definition - What does Sandbox mean?
A sandbox, in computer security, is a security mechanism in which a separate, restricted environment is created and in which certain functions are prohibited. A sandbox is often used when untested code or untrusted programs from third-party sources are being used.
Techopedia explains Sandbox
A sandbox is most frequently used for testing. In this sense, a sandbox is really nothing more than a test or staging server. The goal is to give enough access to allow proper testing while not exposing critical systems to potentially flawed code. In practice, this can take the form of a separate server or mirrored production enviornment.