VBScript is very similar in function to JavaScript, as a language to write functions that are embedded in or included from HTML pages and interact with the Document Object Model (DOM) of the page, to perform tasks not possible in HTML alone. Other web browsers such as Firefox and Opera do not typically have built-in support for VBScript. This means that where client-side script is required on a web site, developers generally use JavaScript for better browser compatibility, since Internet Explorer also has an implementation of JavaScript (known as JScript).
VBScript is a scripting language
A scripting language is a lightweight programming language
VBScript is a light version of Microsoft's programming language Visual Basic
How Does it Work?
When a VBScript is inserted into a HTML document, the Internet browser will read the HTML and interpret the VBScript. The VBScript can be executed immediately, or at a later event.