It means that it is a version of Java that is currently unsupported by either Apple or Oracle and has well know[n] vulnerabilities to exploits. The current supported and secure release is Java 8 build 51.
I found the legacy apps that were not recognizing the newer JRE (Java Runtime Environment) would recognize the JRE that comes in the Java Developers Kit on the Oracle site. Because of its known vulnerabilities to exploits I cannot recommend installing the JRE 6.
NOTE: Oracle has labeled Java 8 Build 51 a critical update. I suspect it patches a newly discovered vulnerability. Keeping Java and OS X up to date are the best protections against malware of all varieties.
JRE is a browser Java Applet plug-in — currently version 8 update 51 (which I thought is a separate issue from the Java install), ie, to my untrained eye they seem to be different/separate entities for different/separate purposes.
What's the story?
