Mainly JavaScripts are used in web sites, to enable some basic dynamic functions, since html can not do that. It is executed on a client-side, so it doesn't put any additional load on the server. That may be a big advantage, or a big disadvantage, depending on what you need. JavaScripts can also be used in making some desktop widgets or PDF files, but it's main use is as part of HTML web site code. Please note the difference between JavaScripts and Java, because as you wrote it I suspect you though that Java scripting is an interpretation of Java programming language.
it can manipulate data, look, and style of a page.. it can also communicate with the server without the need of form submission or page redirection..
hey... JavaScript is a scripting language developed by Sun Microsystems. Javascript has been used to customize web pages. You can customize your web page to check out who's browsing (by reading the viewer's cookies) figure out where else they've been or where they're located and start putting advertisements for your local area or for other interests that you have shown by your past viewing.
Java is a language developed by Sun Microsystems. Javascript is a language developed by Netscape (and probably named to take advantage of the popularity of Java at the time). They aren't the same thing.