What is Java?
If is say it in simple words than Java is a programming language otherwise it?s a combination of three different things java programming language, Java Platform and Java virtual machine.

Java Version
Several changes in original Java, in other words there is many changes have been made in JDK 1.0 since it has been introduced.
So every new version of Java comes with many more new features.

How to find version of Java installed on my computer?
To find out the version of Java installed on your computer, just type
Java ?version

On your command prompt and it will tell you which version of Java you are using.