Native Android
The aptest definition for android is - "Android is a mobile operating system based on a modified version of the Linux kernel and other open-source software, designed primarily for touchscreen mobile devices such as smartphones and tablets."
Evident enough that the software engineering field for developing such apps is known as Android App Development.
Why Learn Android Development
Android Development is low cost and provides high ROI. Since Android has a huge number of clients from increasingly diverse backgrounds, applications are less expensive. Most of the applications are free to download and are also easily available on the play store in comparison to another operating system.
Recommended Reading: Why Learn Android Development
Further Reading
All the great learning resources of COPS Dev group can also be found at COPS Dev Resources.
For frontend resources you should refer CSoC'21 Dev Frontend.