Material Design was launched with Android 5.0 (API level 21). The purpose being to provide consistent look and feel to all the Apps. So your App looks consistent with a Google App like Gmail.
It uses Animation and 3D effects.
Android provides the following elements for you to build material design apps:
- A new theme – Provides a new style for your App.
- New widgets for complex views
- New APIs for custom shadows and animations
Two of the most important Material Design widgets are Recycler and Card Views.
RecyclerView widget is a more pluggable version of ListView that supports different layout types and provides performance improvements.
CardView widget lets you display important pieces of information inside cards that have a consistent look and feel.
In addition to the X and Y properties, views in Android now have a Z property. Views with higher Z values cast bigger shadows and appear on top of other views.
To learn more about the principles of Material Design visit the following URL
Source : Android Documentation
Why Android 