The terms, server-side and client-side code, are quite often heard in the context of Web development.
Client-Side code is run when a website page is viewed by the user. The code is run on the user's computer.
Firstly the client-side code of website's page is downloaded, then run and displayed by the browser.
Examples of popular client-side web languages include Javascript, VBScript, HTML, CSS, AJAX,
Server-side code on the other hand is run on the server, then its results are downloaded and displayed in the browser.
Examples of popular server-side web languages include PHP, Python, Ruby, ASP.NET and... JavaScript!
JavaScript can also be used as a server-side language, for example in the popular Node.js environment
