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.