What is the difference between simple aws lambda and aws lambda@edge ?
Lambda executes functions based on certain triggers. The use case for Lambda is quite broad and there is heavy integration with many AWS Services. You can even use it to simply execute the code via AWS's API and receive the code into your scripts separate from AWS. Common use cases include Lambdas being simply executed and the output received, plugged into API Gateway to serve user requests, modifying objects as they are placed into S3 buckets, etc.
Lambda@Edge is a service that allows you to execute Lambda functions that modify the behaviour of CloudFront specifically. Lambda@Edge simply runs during the request cycle and makes logical decisions that affect the delivery of the CloudFront content.
https://aws.amazon.com/lambda/features/
https://docs.aws.amazon.com/lambda/latest/dg/lambda-edge.html