Amazon S3 or Amazon Simple Storage Service offers scalable and secure object storage via a web service interface. You can easily store and organize exabytes of data for different use cases, including website and mobile applications, IoT devices, big data analytics, data lakes, and more.

When Amazon S3 detects an event of a specific type (an object created, for example), it can publish the event to AWS Lambda and invoke your function in Lambda. In response, AWS Lambda runs your function.

Amazon S3 is object storage designed to store and retrieve any amount of data from anywhere on the Internet. It's a simple storage service that offers industry-leading durability, availability, performance, security, and virtually unlimited scalability at low costs.

You can trigger AWS Lambda on S3 if there are file uploads in S3 buckets. AWS Lambda includes a handler function, which acts as a start point for the AWS Lambda function. The handler consists of the details of the events.