The official document of EFS describes EFS really succinctly. Let's look at it.
Amazon Elastic File System (EFS) is designed to provide serverless, fully elastic file storage that lets you share file data without provisioning or managing storage capacity and performance.
- Managed NFS (Network File System) that can be mounted on many EC2.
- EFS works with EC2 instances with multi-AZ
- Highly available, scalable and expensive.
- Use cases: content management, web serving, data sharing etc.
- Compatible with Linux-based AMIs.(Not Windows)
- Scales automatically and based on the Pay Per Use billing type.