When a user requests a website by typing URL in address bar of browser, the request is accept by the web server which hosts that site. Web Server executes some code to fulfill client request and generate output. The code which is executed at server end

is called server side script and computer languages used to write this script are called server side scripting languages. Examples of server side scripting languages are CGI, ASP and PHP

The response or output of web server is send to requesting client. This response consists of HTML and some other script. The HTML is rendered by browser. Browser also executes the script received from server. This script or small program embedded in HTML is called client side script and we can write this script in client side scripting languages. Client side script is used for client side validation and other operations like drop down menus, moving fonts. For example when user fills in an entry form. To make sure that user has typed all required fields we need to write code to check this before saving it in database. This validation code can be written to execute on server side or client side. If we write this code in client side scripting language this will save time and traffic load between server and client. Examples of client side scripting language are JavaScript and VB Script.