Google sandbox is less known but extremely important phenomenon for newly launched websites. google sandbox acts as temporary filter for new websites before they launched in google search pages.
Google Sandbox is a filter placed on new websites as a result of which, a site does not receive good rankings for its most important keywords or phrases. Even with good content, a site is may still significantly affected by the Sandbox effect. A site is sandboxed when it is new and does not rank for the keyword phrases that are not incredibly competitive in Google.