In a simple word, website development is building the website from scratch or built it with the help of coding. Website design is like decorating a house with a different color and pattern.

In the technical aspect, everything related to server side programming using PHP or ASP.net is development. Designing include user interface development including client-side scripting using javascript too.

Web development is closely related to designing the job and feature as per the functionality. The term development is a continous process because of website development can’t be completed in one day. The basic tools for programming for web programming languages called HTML (Hypertext Markup Language), CSS (Cascading Style Sheets), and JavaScript.
Like building a house, websites designing is different from one another. There’s really a wide range of pre-built and custom theme available, a web developer can choose from there. Website development is very construction and maintenance work in web development.

Web development can also be involved in working with a content management system (CMS) like WordPress, Drupal. These are the programs built to manage websites.