What is "materialize"

Materialize is a css and javascript framework that implements the Material Design guidelines. Material Design was created and designed by Google, is a design language that combines the classic principles of successful projects along with innovation and technology. Google’s goal is to develop a design system that lets you unify the user experience across all your products on any platform.

It is an open-source project and besides its maintainers has the help of the community for its development. Materialize is not maintained by Googles and nor its employees, is a project totally independent of the company.