The Order Orthoptera is formed with two groups: Ensifera and Caelifera. In general terms they are known as locusts and crickets respectively
There are several differences between these suborders. But the most basic one which lets us know what it is is the length of the antennae. More than 30 segments correspond to crickets, less than that to locusts. Roughly speaking, long antennae, crickets; short antennae, locusts.
If both locusts and crickets are famous for something is their capacity to jump. Of the three pairs of legs only the posterior one, which is very strong, is prepared to jump. It has springs which together with the muscle allow th storage of energy which ejects it like a catapult when it is released. Jumping is a way to escape, fight or simply jump.
Another typical characteristic of this order is the sounds they produce rubbing parts of the body. In crickets the stridulating mechanism is in the anterior wings. In locusts it may be either in the wings or the legs. Singing is used to form pair or as a sign of alarm or agression. Good singing implies good hearing and this sense is located differently in locusts and crickets. Crickets have their "ear" in the frontal tibia and locusts in the first abdominal segment.
It is to be noted that there are exceptions to the rule and that some characteristics may be absent, for instance, stridulatin mechanisms.