In web development, frontend and backend refer to the two main parts of a website. The frontend is the part of the website that the users interact with while the backend is responsible for storing all the data and code of the website. Frontend developers focus on designing the visual elements of a website. This includes everything from the layout and structure of the page to the colors and fonts used. Backend development is about building the server-side components of a website or application. This includes everything from database design to server-side logic. A backend developer must have a good understanding of server-side programming languages and be able to program in PHP, Ruby on Rails or Python.