Erm,
Also, when you say County Jail or State Pen, what's the difference there?
As Sauron says, the difference is usually statutory. The kinds of crimes that are going to get you into the state prison system are worse generally than the County where you committed them usually involving longer sentences. There are some exceptions, such as overcrowding forcing officials to put some in one or the other. For example, you could be awaiting trial in one with a sentence expected to get you into the other. Culturally, the prison takes the dangers of county jail a magnitude further. The kinds of people who are facing long sentences or who are never going to get out, career criminals, people who cannot seem to stay out of the criminal justice system or who actually want to be there. The class of people has sometimes been described as convicts vs. inmates.