What is the essential difference between a sandbox and a virtual machine?

The principles of the two are completely different. Sandtable is a security software, somewhat similar to the shadow subsystem. It can isolate the isolated environment in which the software runs in the system and avoid the change of the system and data by the software. Besides protecting the system, it is also a good choice for testing software. Virtual machine is just a system software, which can simulate one or more "real" hosts from the bottom. The reason for saying "real" is that these hosts have hardware (virtual devices) and can install systems. There is no problem in installing software and surfing the Internet in the virtual system, and it is no different from the real system in use (of course, the performance is definitely not as good as the real system). These "real" hosts are isolated system environments, and all the hosts are in them. Besides software testing, you can do many tests and experiments. Simply put, compared with virtual machines, sandboxes can only complete simple protection functions, while virtual machines can completely simulate the real system environment.