Almost as old as the internet itself are efforts from some parts of the world to sensor it. This goes beyond stopping your kids from accidentally accessing porn. It refers to people, organizations and governments who aim to stop other citizens from accessing information that would harm their efforts to have those people believe what they want them to.
If that sounds confusing, think of it as propaganda in reverse. While propaganda places partial truths and untruths in front of citizens, internet censorship takes away some level of access to the truth.
Of course, there are many who believe this is a human rights violation.