What are gypsy and travelers ?

What are gypsys? why are they called travelers ?what do they do for a living and how do they live ? how come their life style looks poorly but at the same time looks like they are wealthy? how do they make those huge expensive weddings? Why are their weddings and dresses style bring so much attention ?how come they look like costumes and exaggerate? What do they live for how do they live ? How come they get rejected a lot? Please help I would like to know they seem interesting