HTML page source code refers to the underlying structure and content of a web page, written in the Hypertext Markup Language (HTML). It is the code that is used to create the visual layout, text, images, and other elements of a webpage. This code is typically viewed by developers and designers to understand how a webpage is constructed and to make any necessary changes. It is also used by search engines to index and display web pages. HTML page source code is essential for creating and maintaining a functional and visually appealing website.