Amazon Elastic File System (EFS) provides shared, persistent, and elastic storage in the AWS cloud. It offers features such as simultaneous access from multiple clients, AWS Lambda integration, and supports big data workloads, machine learning, and serving web content. EFS operates in two performance modes: General Purpose mode, which provides low latency for most use cases, and Max I/O mode, which provides higher IOPS at the cost of additional latency. The storage class determines the availability and costs associated with storing data, with Standard being the default and One Zone providing reduced costs but lower availability. Monitoring EFS metrics such as file size, latency, I/O utilization, throughput, and connection count is crucial to ensure the performance and health of applications accessing shared storage.