It was created starting from two plates made of steel and carved by hand with hammer strokes until it reached a “sound sculpture” in which the resonance and the harmonics of the different notes it composed were in perfect balance with each other. In the upper part it presents a Ding (the central "bass") and the 7 or 8 a around it are the notes of the musical scale. Below there's the Gu, it presents a round slot (like an Indian Gatham) that allows you to activate the Helmotz resonance.
In general, the techniques to play the instrument are percussive (typical of Darbuka movements, Indian Tabla, frame drums, etc.), although much more delicacy is required. It also presents its unique peculiarities such as rubbing and clutches on the Ding in search of the resonance of the harmonics or air shifts after the "touch" on the note.

This instrument is at the beginning of its life and therefore in continuous evolution both in the techniques used to play it and in the way it's built.
Some Handpan players experiment with special techniques of speed on the notes, others play it "vertically" with the instrument held between the knees, to ensure that on the one hand the melody is played with the notes and on the other produces a more "percussive" sound and exploit the entry and the exit of air into the cavity of the Gu.
More and more often, us handpan players, we collaborate with classical instruments (such as violin, piano and flute) or ethnic ones (such as didgeridoo, Andean flutes or Asians, Indian tabla and African percussion) and this instrument is increasingly been seen in drummers and percussionist sets. Even the musical styles that the Hang applies to are vary and they spread from Flamenco to Jazz and from World music to meditative music.

Regarding the instrument struction, after the original Hang of the Panart, many artisans all around the world have started to develop new processing techniques and experiment with new materials, some with excellent results.

Nowadays you can see handpans with 9, 10 or more notes and even additional ones at the bottom (GU).
The name of the family of these instruments was initially defined as HANDPAN, but terms such as sound sculpture, pantam, dome, harmonic disc or ufo are also often used to descrive this instrument.
Given the complex and slow craftsmanship and the low number of manufacturers that build Handpans, it is very difficult to find one and the wait is usually very long.
However, various artisans are emerging in different parts of the world, with more or less experience granting different levels of quality of the raw materials and the sound. The choice must always be therefore accurate and very personal.

You can see these two small documentaries on Nobuya Yamaguchi, a Japanese sculptor and builder of Handpan based in Israel.

Live Metal Art 1
Live Metal Art 2

and this of a talented Russian producer:
Birth of a russian handpan

Possible applications in music therapy are also being tested; what is for sure is that it produces in the listener a great sense of well-being and relaxation thanks to the dreamlike atmosphere of its main percussive sound but also soft, harmonious and melodic like a harp, a marimba or a bell.
There is a feeling that the sound comes from "all directions". Children, particularly, are very much attracted and stimulated by its calming sound.

More info on the original Hang here:
HANG
Wikipedia