So What is JRE??
JRE is basically physical implementation of JVM which includes JVM & other libraries need to run code. JRE is just one implementation provided by sun. Many other implementation also exist released by other companies as well.
JDK is basically java development kit which actually required to develop java applications.
Its pack is having element like JRE, libraries & other java development tools required.
tools for compiling, running, performance management etc.
So finally about Java .
Team of Engineer called Greem Team consist of members named James Gosling, Mike Sheridan, and Patrick Naughton initiated the Java language project in June 1991. originally it was developed for embedded system & it named as Greentalk which then rename to oak ( was registered with oak technologies) then changed to Java as it was was island of Indonesia & producer of coffee.
Some Key versions of Java