What is Authorization Bill?

Legal Definition
An authorization bill is a type of legislation used in the United States to authorize the activities of the various agencies and programs that are part of the federal government of the United States. Authorizing such programs is one of the powers of the United States Congress. Authorizations give those things the legal power to operate and exist. Authorization bills must be passed in both the United States House of Representatives and the United States Senate before being signed by the President of the United States in order to become law. They may originate in either chamber of Congress, unlike appropriations bills, which must originate in the House. They can also be considered at any time during the year.
-- Wikipedia