A long time ago in Web terms Netscape made it possible to trigger automated things to happen on Web pages. Originally, it was called Mocha, LiveWire and LiveScript. Then it was renamed to make it sound like it had something to do with Java even though it doesn't.
- make things appear or disappear
- make things move or change size
- adapt Web pages to different screen sizes and shapes
- make checks on data entered into forms on Web pages
- create additional Web page features such as clocks, calendars and silly tricks with mouse cursors
- get and manipulate data
- much more