The instances that can be used in Amazon EC2 are:
1. Standard Instances: It provides small instances, large instances, extra large instances that give various configuration options from low range to very high range like Computing power unit, memory, processor, etc.
2. Micro Instances: It provides small consistent resources like CPU, memory and computing unit. It provides the resources to the applications that consume less amount of computing unit.
3. High Memory Instances: It provides large memory sizes for high end application and it includes memory caching applications as well.