The Wikipedia supplies this information:

The Kachin people are a group of ethnic groups who largely inhabit the Kachin Hills in northern Burma’s Kachin State and neighboring areas of China and India.

More than half of the Kachin people identify themselves as Christians — while a significant minority follow Buddhism and some also adhere to animism. Kachin state is also known as the land of jades and gold.

The main subgroup is the Jingpo, for whom the term Jinghpaw (Jingpo) and Kachin are considered synonymous. However, by Myanmar’s official designation, the term Kachin includes a variety of different linguistic groups with overlapping territories and integrated social structures. These are notably the Rawang, the Lisu, the Zaiwa, the Lashi/Lachik and the Lawngwaw as well as the majority Jingpo.

Such definitions carefully distinguish Kachin and Shan (Tai) peoples though some Kachin people have defied the Western expectation of lineage-based ethnicity by culturally “becoming Shans” (Leach 1965).

Behavior and traditions
The Kachin people are traditionally known for their fierce independence, disciplined fighting skills, complex clan inter-relations, craftsmanship, herbal healing and jungle survival skills. In recent decades, their animist beliefs have been largely supplanted by embrace of Christianity, while traditional animist emblems and pursuits have been largely re-directed into folkloric events such as the annual Manao festival in Myitkyina.

The Kachina National Organization website says “Kachin in Burma are estimated to number between 1 - 1.5 million.”