Here is what some of those words mean in the context of former Secretary of State Hillary Clinton's emails.

The Inspectors General for the State Department and the intelligence community issued a statement saying Clinton's personal email system contained classified information. This information, they said, "should never have been transmitted via an unclassified personal system." The same statement voiced concern that a thumb drive held by Clinton's lawyer also contains this same secret data. Another report claims the US intelligence community is bracing for the possibility that Clinton's private email account contains multiple instances of classified information, with some data originating at the CIA and NSA.

A Clinton spokesperson responded that, "Any released emails deemed classified by the administration have been done so after the fact, and not at the time they were transmitted." Clinton claims unequivocally her email contained no classified information, and that no message carried any security marking, such as Confidential or Top Secret.

The key issue in play with Clinton is that it is a violation of national security to maintain classified information on an unclassified system.

Classified, secure, computer systems use a variety of electronic (often generically called TEMPESTed) measures coupled with physical security (special locks, shielded conduits for cabling, armed guards) that differentiate them from an unclassified system. Some of the protections are themselves classified, and unavailable in the private sector. Such standards of protection are highly unlikely to be fulfilled outside a specially designed government facility.