Chromium is a free and open-source codebase for a web browser, principally developed and maintained by Google. Google uses the code to make its Chrome web browser, which has additional features. The Chromium codebase is widely used. Microsoft Edge, Opera, and many other browsers are based on the code.

Why did Google release Chromium?

This was a “platform play”. In their release announcement, the Chromium team explains their reason for publishing the code under a permissive BSD license. Primarily it's because one of the fundamental goals of the Chromium project is to help drive the web forward.

Why is Google Chromium bad?

While Chromium is a legitimate browser, its open-source code has made it unstable, full of bugs and a target for spreading viruses.