data is unclassified or classified. Unclassified means anyone can see it.
Classified information means it is not revealable to people who have a need to know. There are several levels of classification:
For Official Use Only. This means while it may not be terribly classified, its dissemination is generally limited to those who have a need for it.
in the US, we have Confidential, Secret, and Top Secret. They all have different restrictions on who can see it. And just because you have a security clearence, does not mean you can see anything that is within your clearence rating. There are several other sub categories I will not go into.
ITAR can apply to both classified and unclassified data.