It can be a JRE or a JDK. JRE are used to run java programs and JDK are used for java development.
The 1.5 part means it is java 5 and the 0_15 part means it's update 15. It is old and it is better to use
java 6 because java 5 has reached it's EOSL (End of Service Life).
"Any fool can write code that a computer can understand. Good programmers write code that humans can understand." --- Martin Fowler
Please correct my English.