What is a basic functionality of browsers?

Browsers primarily function to take HTML documents and render them into viewable webpages. This involves interpreting the HTML code, along with associated CSS and JavaScript, to display text, images, and other media as users expect to see them in a visually coherent format. The browser acts as a bridge between users and the web, translating the code into a graphical interface that can be interacted with.

The other options, while important aspects of web technology, do not directly describe the core functionality of a browser. Creating web content pertains more to development tools and practices rather than the browser itself. Securing websites from threats involves security measures and protocols that go beyond the browser's basic rendering functions, falling under the domain of web security and server configuration. Lastly, developing web applications is the realm of developers who write the code and deploy applications, which browsers then render and execute for the end user.