What is the right to access information?

I am assuming that you are asking about the right to access government information.  This is a matter of federal and state statutes.

The federal statute that allows and restricts access to information is the Freedom of Information Act (FOIA). It applies strictly to federal bodies, Congress, for example, the Department of State, and  various federal agencies such as the Federal Aviation Agency or the Centers for Disease Control.  Many people misunderstand this and try to seek FOIA information from state agencies, but this statute is completely inapplicable to those.  As a general proposition, the statute allows the public access to most government documents, with exceptions carved out for areas such as national security, personal privacy, and the federal enforcement of law. For example, if the United States Attorney General's office is investigating someone suspected of a crime, information on that is likely to be protected, since the investigation could be compromised by the release of information about it.  Many citizens and reporters do make FOIA requests, and the overwhelming majority of requests are granted or partially granted, but there is always a backlog of requests to process.  Reporters often use these for their own investigative reporting.  This is an important aspect of a democratic government, the idea that the workings of government of the people should be transparent to the people.

Each state has its own statute that controls what state records are accessible to the public. In Pennsylvania, as an example, the statute is called the Right to Know Act, and a special office has been set up to deal with all the requests that come in, the Office of Open Records.  There is "a presumption of openness" in the statute, and all state agencies, offices, and departments are subject to it, as well as local government bodies.  The exceptions are much like those of the FOIA, although national security is not generally at issue, since that is not the function of state government.  Personal information such as social security numbers or law enforcement information that would harm an investigation are exempt. Whatever state a person lives in, if he or she seeks records from the government, the state statute must be reviewed to see if the records are actually accessible. 

I should also note that these statutes actually control the release of records, not precisely "information."  The FOIA and the Right to Know Act do not compel anyone in the government to answer questions, for instance, either in writing or orally.