What does max/total/free memory mean for a JVM (and in JON)?

Issue

• When monitoring the memory use of a JBoss instance/JVM please explain what the metrics JVM max / total / free memory mean.
• We have observed dramatically different values being reported by the JBoss EAP 6.1 management GUI for JVM memory usage compared with those reported by JON. In particular the metrics for heap and non-heap memory usage.