Being the upstream project for Google Chrome, Chromium serves as the foundational codebase. Developers can use Chromium to build their own browsers, adding unique features or customizing the user experience to suit specific needs. This flexibility makes Chromium a popular choice for various browser derivatives like Opera, Microsoft Edge, and Brave.
In contrast, Google Chrome is a proprietary browser developed by Google that builds upon Chromium's codebase. While Chrome incorporates all the core functionalities of Chromium, Google adds proprietary features, branding elements, and services that enhance the user experience. These additions are not available in the open-source Chromium project and are part of what differentiates Chrome from its open-source sibling.