What is the difference between a leaf hopper and a grass hopper?

"Locusts are part of a large group of insects commonly called grasshoppers which have big hind legs for jumping. Locusts belong to the family called Acrididae [,short-horned grasshoppers]. Locusts differ from grasshoppers in that they have the ability to change their behaviour and habits and can migrate over large distances. As Desert Locusts increase in number and become more crowded, they change their behavior from that of acting as an individual (solitarious) insect to that as acting as part of a group (gregarious). The appearance of the locust also changes: solitary adults are brown whereas gregarious adults are pink (immature) and yellow (mature). Up until 1921, it was thought that the Desert Locust was actually two different species of locusts." http://www.fao.org/ag/locusts/en/info/info/faq/