Definition of the Sandbox
The Sandbox term is used for the environment where you can test, experiment, and learn about the product or service.
The Myth about Google Sandbox Effect
Many industry experts assume that this is the place where sites are kept till they get mature enough to be included in the top rankings for a particular keyword.
The other myth of sandbox is that the site is kept here because of some penalty and before deindexing from Google.
The Truth About the Sandbox
The truth is that there is no official announcement about the Google Sandbox effect except, that it is a community bringing local tech experts and Googlers together. You can see it here.
Google Sandbox is inspired by the software development term “sandbox”- an environment for experimentation, testing, and learning. Whether you’re early in your career or a seasoned professional, a software engineer or an accountant, the Sandbox program reflects a wide range of professional talent and focus areas.Source: Google Sandbox