What is the primary purpose of plug-ins in web browsers?

Plug-ins serve a crucial role in enhancing the functionality of web browsers, particularly in the context of multimedia content. The primary purpose of plug-ins is to enable browsers to play multimedia elements such as videos, audio files, and interactive graphics that are embedded in web pages. This capability allows users to experience rich media without needing to switch to separate applications. For instance, without a plug-in, a web browser would not be able to render specific video formats or interactive content found on various websites, limiting the user experience.

In contrast, creating new web pages is a function typically associated with web development tools rather than browser plug-ins. Increasing browsing speed is affected more by the browser's core functionalities and underlying hardware rather than by plug-ins. As for security, while certain plug-ins may offer additional protection features, the primary function of plug-ins is focused on enhancing multimedia capabilities rather than providing comprehensive protection against malicious software. Thus, the correct answer highlights the main function of plug-ins in enriching user interaction with web media.