The frontend is the part of a website or app that people see and interact with. It includes things like pages, buttons, menus, and forms.
When you choose an item in a menu, the frontend shows the choices and responds to your click. It may also ask another part of the system for information, such as a list of products.
Frontend work focuses on the visitor's experience, but it is connected to other parts behind the scenes. A page can look right while still needing checks to make sure its actions work.