Material design
You might have heard of material design, but what exactly is it? The objective of material design is quite simply to achieve beautiful user interfaces. It is also, however, about making these user interfaces consistent across Android devices. Material design is not a new idea. It is taken straight from the design principles used in pen and paper design, like having visually pleasing embellishments such as shadows and depth.
Material design uses the concept of layers of materials that you can think of in the same way you would think of layers in a photo editing app. Consistency is achieved with a set of principles, rules, and guidelines. It must be stressed that material design is entirely optional, but it also must be stressed that material design works, and if you are not following it, there is a good chance your design will be disliked by the user. The user, after all, has become used to a certain type of UI and that UI was most likely created using material design principles...