Need java start help for a beginner?

hey people, i'm just beginning to learn java. i know c c++ etc, but nothing about java. my lecturer was taking particles today and my head just started spinning after i herd some weird terms. does java have a compiler just like c? what the heck is JDK, J2SE, JRE or runtime environment, why is java called a stand alone language (whatever that is)? pls help, really lost here...