What does Java run, operate, or do?

Figure I might as well get what I need on the way out the door.

I have Googled it and either gets near misses or nebulous explanations. I understand Java is a language, as C+ and C++, etc. though not exact as them. Google sent me to sites that says what industries etc. make use of Java, or which gadgets make use of Java but I have not really found any that says ”Java is used for this, this and that”. I JUST KNOW someone here has an inkling of what it does. Does it compile, crunch numbers, arrange data, track data, what? When you GA someone and it shows up immediately or soon after on the Fluther leaderboard on the right, was that an example of Java, or something else? Where is that Ben guy when you need him? If I read right, Java is a server side application where JavaScript is a client side or browser based application, but Java does something, what does or can you do with it?