If you are interested in learning user interface and user experience design techniques, then a good place to start, given the wealth of useful knowledge shared, is the Material Design site by Google.
We challenged ourselves to create a visual language for our users that synthesizes the classic principles of good design with the innovation and possibility of technology and science. This is material design. This spec is a living document that will be updated as we continue to develop the tenets and specifics of material design.
I consider myself fairly seasoned when it comes to interaction design, but if for no other reason than learning how to articulate the points made, Material Design has plenty of learnings, information and inspiration.