Steven Quartz Universe or Steven Universe (called by lazy people that are too lazy to say "Quartz") is a half human half gem who possesses the power of an alien species known as the Gems.
He has a TV show about himself called, well, Steven Universe.
When a Gem named Rose Quartz gave birth to an offspring whose name as we know it is Steven Quartz Universe, Rose died because of some reason that the creator of the show wouldn't tell us because of an experience working with the creator of Adventure Time. Anyway, Steven is yet to discover his inner gem powers. All he can seem to do is summon a shield for a few seconds at a time. Every time he discovers his new power, he would use it for fun then he will eventually end up in trouble. It's a cliche.