A sandbox is a cyber security mechanism which separates running programmes to prevent infection of the system.
The sandbox is used to execute code that is untested or programmes that are untrusted. These may come from unverified third parties or untrusted websites.
As these programmes or code may contain viruses, the sandbox provides a safe environment for the virus to execute in.
Because the sandbox uses a tightly controlled set of resources and does not provide the ability to access the network or inspect the host system, the threat if there is one is contained within the sandbox.
It is extensively used by security researchers to test threats, but is increasingly gaining prominence as a form of protection.
Virtualisation overall is seeing increasing interest as a way of dealing with cyber security threats, with companies using the isolation of these threats to protect the system or device as a whole.