At the Google I/O Conference back in 2014, Google announced Material Design, their new design language. They have since converted much of their popular applications to adhere to this new spec in an effort to provide a consistent experience. Now they are trying to convince you to follow along as well.
What is Material Design?
After a visit to the official Material Design spec, you will immediately get a feeling of ultra-modern minimalism. Basic shapes and flat colors are the theme here. Going through the documentation is quite an experience. I recommend taking a look for yourself, but I will summarize it here.