What is the veil of ignorance? What societal rules (be specific) does John Rawls think we would establish from behind the veil of ignorance?

What is the veil of ignorance? What societal rules (be specific) does John Rawls think we would establish from behind the veil of ignorance? Is Rawls correct that this would make for a more just society? Give an argument.

(Please provide as much information as you can regarding this question and any examples that is easy to understand would be highly appreciated.)