What does "tenure" mean? I often find academics with tenured bracketed beside their position. What is meant by a tenured position? Is this different from a permanent teaching position?
In short, tenure means that you cannot be fired (you have a very permanent position).  For more details, look at this question:
In practice, how secure is a tenured position in the US?  In particular, look at the first link in the first answer to that question, which is an article in Science that talks about the role of tenure.