What is Java?

I have this installed on my computer and my antivirus tagged a zip file withing java's folders as a trojen. Is this needed for the computer to run? I have Win XP. Also can I delete this from the computer? I have Java 2 Runtime Enviroment SE v1.4.2_09. Also have Update 5 and update 6 installed. These are taking approx 420MB of space. Thanks for the help

[362 byte] By [Girangera] at [2007-10-2 11:47:40]