Building larger serverless applications can be tricky - creating many lambda functions as well as other resources such as DynamoDB tables, S3 buckets, API Gateways takes quite a lot of time if we were to do it manually from AWS Console. Not to mention other problems such as redeploying the app to a different region, reviewing the infrastructure etc.
AWS Serverless Application Model (AWS SAM for short) simplifies a lot of those issues.
Built with with best practices in mind it allows you to:
Take a look at WTF is AWS SAM in this quick 2 minute lesson