The following was taken from:
Visual TM / Read Less, Learn More TM / JavaScript TM
IDG Books / Murdock Publishing / Copyright 2000
Web page files, written in the Hypertext Markup Language (HTML), define how elements such as text, tables, and images will appear when viewed in a browser. HTML deals only with static elements.
JavaScript is a scripting language that can co-exist with HTML in a Web page file. It can be used to add interactivity to a Web page. This interactivity enables the Web page creator to dynamically control the Web page elements.
You can also use JavaScript to change Web page elements as the user interacts with the Web page. For example, you can set the text displayed in a form’s text box to update when the user clicks a button. JavaScript can run in a browser without any additional tools.
JavaScript is the most popular client-based Web scripting language because
it is supported on both Netscape Navigator and Internet Explorer, but you
can use other scripting languages to add interactivity to a Web page.