For those of you who have already used another web framework as a Bootstrap, do not you feel disoriented with MDL.
If Google already has a set of components Material Design available for developers in its Polymer framework, MDL come to focus on design. While the elements of Polymer they can be used individually or together to create a site inMaterial Design. MDL in fact, It is only a specific set of sources, animations, etc and their experience is compatible with Chrome, Firefox, Opera, Safari and Microsoft Edge.
Source: Google Developpers