App2Container is a tool that automates the process of creating container versions of existing applications, streamlining the transition to containerized infrastructure without altering the application's original source code. The other choices, such as Fargate, Elastic Container Service (ECS), and Elastic Kubernetes Service (EKS), provide platforms to run containers but do not assist with the actual containerization of existing applications. Elastic Beanstalk can deploy and manage applications in the AWS Cloud, but it is not specialized in containerizing applications. Lambda is a serverless compute service and is not used for containerizing applications.