Amazon Elastic Container Service (ab. ECS) is a scalable, managed orchestration system that launches and governs multiple containers in a cluster. It is not constructed on Kubernetes. Amazon Elastic Kubernetes (ab. EKS) permits you to design and set off Kubernetes on AWS without manually installing Kubernetes on EC2.
Also, an important difference between them is in the pricing model. When using ECS, there is no additional fee for launching EC2. Users disburse only for the services they create to work with the application, store and run it.