Goa is a place in India. It is on the coast, but is not an
island.
Goa is a form of Techno music, more specifically a form of trance that was born in Goa, India in the late 1980s to early 1990s at outdoor parties. It is definitely dance music not ambient, generally in the range 140 to 150 bpm, with 148 being most common.
It is trippy, acid and is characterised (at its best) by multiple melodic layers and heavy use of the 303 and LSD and a fascination with fluorescent Hindu gods.
Try the following albums for goa. This is not a definitive guide, just a sample. Many bands that made goa later made psy-trance, ambient or even dub.
Later on, (circa 1996) goa evolved into Psychedelic Trance, by a process of exporting the sound to the (mostly indoor) parties in Europe and mutating it slightly into something darker and less uplifting, with a more complex, more European, less melodic and less mystical sound. By 2001, the ever-reinventing genre has already passed though Psychedelic Trance and Psychedelic Techno. The beat has slowed to about 140.