Syngonium are climbing aroids sold as compact bushy plants, which is not what they naturally are. Left alone they become vines.
The shape change
Juvenile Syngonium leaves are simple arrowheads, which is where the common name comes from. As the plant matures and starts to climb, the leaves divide into three, five or more lobes and look like a different plant entirely.
Nurseries keep them in the juvenile form by pruning. If you want the bushy arrowhead look, keep cutting the vines back. If you want the mature form, give it a moss pole and let it climb.
What every Syngonium wants
Medium to bright indirect light, soil that dries slightly between waterings, and nothing special in the way of humidity. They grow fast and forgive most mistakes.
Syngonium are toxic to cats and dogs.