what is this file extension
 

what is this file extension and what do i do with it?

.jar

its a java file, more then likely i think you will need jre to use it but i could be wrong
http://java.sun.com/j2se/1.3/docs/guide/jar/jar.html
some reading on it mostly technical info

yes, .jar are Java ARchives. They are an [misspell]agrupation[/misspell] grouping of all your .class archives (binary code) with some other configuration files (like manifests [plain text]). (If my mind doesn't fail me, I think it's almost equivalent to a .zip file).

Yo can execute a .jar archive if you have a virtual machine that understands the java language. So, you can install the official jre (http://java.sun.com) or kaffe (http://www.kaffe.org/) (I'm sure there are more virtual machines, but I only know this two)

With the official jre installed, you can run your app with:
java -jar file.jar

You are right, its a java archive file and to run it you need to have java installed.

agrupation??
Webster's online does not think this is a word---nor do I. I infer that it has to do with grouping or aggregating.

Computer people LOVE to invent words.....One of my favorites is "disambiguate"
OOPS--my mistake---that one is in Websters (but I bet a computer guy put it there.....;)

:study: jeje, you're right.. That's not English, maybe Speranto?

I've to recheck my locale :p