SAM Local takes all the good parts of SAM and brings them to your local machine.
It lets you develop and test your AWS Lambda functions locally with sam local and Docker.
It lets you simulate function invocations from known event sources like Amazon Simple Storage Service (S3), Amazon DynamoDB, Amazon Kinesis, Amazon Simple Notification Service (SNS), and more.
It lets you start a local Amazon API Gateway from a SAM template, and quickly iterate on your functions with hot-reloading.
It lets you quickly validate your SAM template and even integrate that validation with linters or IDEs
It provides interactive debugging support for your Lambda functions
https://aws.amazon.com/blogs/aws/new-aws-sam-local-beta-build-and-test-serverless-applications-locally/ (2017):