Material Base — is a base theme for Drupal 7, 8 and 9, which implements Material Design concept by Google.
A base theme meant that it is like a set of components, which can be easily combined for making beautiful Drupal themes instead of making it from scratch.
But Material Base requires base knowledge of Drupal theming system as well as base knowledge of CSS. And even better if you familiar with SASS.
Material Base — is the theme for themers.