The desired degree of secrecy about such information is known as its sensitivity. Sensitivity is based upon a calculation of the damage to national security that the release of the information would cause. The United States has three levels of classification: Confidential, Secret, and Top Secret. Each level of classification indicates an increasing degree of sensitivity. Thus, if one holds a Top Secret security clearance, one is allowed to handle information up to the level of Top Secret, including Secret and Confidential information. If one holds a Secret clearance, one may not then handle Top Secret information, but may handle Secret and Confidential classified information.
Source: https://en.m.wikipedia.org/wiki/Classified_information_in_the_United_States
