Jaz or Jasper is a Homeworld gem that fought in the war. She's a surviver of Her quadrant and the leader her squad.
How they survived is that she just barely missed the diamonds attack while trying to retreat. Since she was so close to the planet when the attack happened, Her Ship crashed back on earth trapping then on the planet for many of Year's.
From, The end of the battle for the earth To The events of Steven universe, Jaz Hid from rose quartz and whats left of her army. But by hiding they learned of the beauty the plant has to offer. So she hid among humans and the animal life, Coexisting among them.
She had many name's Jase, Iris, Jasmine, But Jaz is what she goes by in present times. Theres even legends of her eternal Wandering, How she's a ghost who has unfinished business.
The survivers of her pod are 2 peridots, 1 Bismuth, and 1 Jasper. They basically just travel around, but currently are located in hawaii.
'This is before Steven universe Season 2'