Function as a Service (Faas) is the idea of running your application code via a serverless architecture and is event driven. Your application code is deployed and executed on a platform hosted and managed by the cloud provider. In the case of AWS this is called Lambda. The execution of the Lambda is triggered by a pre-defined event in your solution. For example a new object is placed into your S3 bucket and this event triggers your Lambda function to process the data associated with the new object.