What is the difference between Amazon ECS and Amazon EC2?

Question

I'm fairly new to AWS, I understand that EC2 is like a remote computer I can do pretty much everything I want. Then I find ECS, I know it is a container management service but I'm confused how these two are related to each other.

If I already have an EC2 instance, and then I start ECS, does it mean that I have two instances?

Answer 1

No, if you have an instance and then you start an ECS cluster, it does not means that you'll have two instances. 

EC2, as you already understand, is simply a remote virtual machine that you can launch.

ECS, on the other hand, is a logical group of EC2 instances on which you can run an application without having to scale your own cluster management infrastructure because ECS manages that for you.

If you have an instance, then you launch ECS, you'll have that one EC2 instance only. If you go ahead and register that EC2 instance to ECS then your instance will become a part of the ECS cluster but you will still have a single EC2 instance in that cluster.