Google Sandbox is a Google algorithm which tracks the methods you used to build backlinks for your blogs or websites. Google Sandbox tracks the IP address of your computer and will notice how much and how frequently you are building a backlinks for your blog/website.
This is the place where the new and less authoritative websites were kept for a definite time period, till their establishment in the search results. This may happens due to the building of so many links within a short time period.
The Google sandbox refers to a commonly held belief that Google has a filter that places all new websites under restrictions for a certain period of time to prevent them from ranking in searches. The idea behind the Google sandbox is that newer websites are not as much relevant as older sites, and they are also more likely to be spam. For this reason, new websites are restricted and allowed to mature before being allowed to rank well, much as a young child is placed to play in a sandbox by his or her caregiver. Google will neither confirm nor deny the existence of the sandbox, it is widely accepted as fact.
Websites can be in the Google sandbox for different amounts of time, generally for six months to a year. It is extremely difficult to avoid having a brand new domain being placed in the sandbox.