In Comupter Secuity: from https://en.wikipedia.org/wiki/Sandbox_(computer_security)

In computer security, a sandbox is a security mechanism for separating running programs. Sandboxing is frequently used to test unverified programs that may contain a virus or other malicious code, without allowing the software to harm the host device.

A sandbox typically provides a tightly controlled set of resources for guest programs to run in, such as scratch space on disk and memory. Network access, the ability to inspect the host system or read from input devices are usually disallowed or heavily restricted.

In the sense of providing a highly controlled environment, sandboxes may be seen as a specific example of virtualization.

In Software Testing: from https://en.wikipedia.org/wiki/Sandbox_(software_development)

The concept of the sandbox (sometimes also called a working directory, a test server or development server) is typically built into revision control software such as CVS and Subversion (SVN), in which developers "check out" a copy of the source code tree, or a branch thereof, to examine and work on. Only after the developer has (hopefully) fully tested the code changes in their own sandbox should the changes be checked back into and merged with the repository and thereby made available to other developers or end users of the software.

The term sandbox is commonly used for the development of Web services to refer to a mirrored production environment for use by external developers. Typically, a third-party developer will develop and create an application that will use a web service from the sandbox, which is used to allow a third-party team to validate their code before migrating it to the production environment. Microsoft, Google, Amazon.com, PayPal, eBay^[ and Yahoo, among others, provide such services.