What is sandbox solution
Sandbox is a restricted environment where programs are deployed with restrictions. It plays valuable role for developers to test their application by using sandbox solution. Once this is tested it can be later deployed to full use in the farm.
Solution that are deployed into sandbox are called sandbox solutions.
Advantages
If farm is load balanced.
Release code which is fully not tested for production release.
Less bottleneck for farm administrator as this can be managed at site collection by administrator to it.
Disadvantages
First decide whether you want this solution? as using this solution does has impact on performance of the servers. As the farm using sandbox does have more process load than a farm without this.
Code Access Security (CAS) limits the operations that the code can perform
How to use
Activate SharePoint 2010 User Code Host service(SPUCHostService.exe,) on server you want this solution. Should be done by farm administrator
Sandbox Code Services
Sandbox can be applied at the root of site collection level.
Members of the site collection administrators group can deploy sandboxed solutions
Governance for sandbox
Before deploying think of below
When should the solution be blocked or unblocked?
When to release the solution to production?
Who should be given access, deployment rights etc?
Adding / Blocking /Load Balancing for Sandbox
This can be done via CA – System settings
Special Thanks :Amarprit Jaspal