Amazon SQS (Simple Queue Service) is a fully managed message queuing service that enables applications to communicate by sending messages between different components. It helps decouple microservices, distributed systems, and serverless applications, allowing them to work independently and efficiently. With Amazon SQS, developers can send, store, and receive messages at any volume without losing messages. It supports two types of queues: standard queues, which offer high throughput and at-least-once delivery, and FIFO (First-In-First-Out) queues, which ensure that messages are processed in the exact order they are sent.