Course introduction

Server and client-side

When you write in an URL and hit enter in the address bar of your web browser, a request is sent to a sever where the site is located. The server returns a response to your browser containing the content to be shown by the browser as illustrated in the figure below.

We typically divide the technologies and programming languages involved in web-development based on whether they primarily are being executed on the server or the browser (client). The former is referred to as server-side, and the latter, client-side. Common examples of client-side languages are HTML, CSS, JavaScript, and JavaScript frameworks such as Angular and React, and these are being executed by the browser on your computer. Server-side languages such as PHP are in contrast executed on the server, before a response is sent back to the client, often in HTML format which can be treated by the client browser.

The server typically also communicates with a database server. For instance, PHP code executed on the server can be used to fetch data from a database. When a client request a file from the server, the PHP-code on the server is executed, fetching the data from a database, and the result is returned to the client as seen in the figure below.