where and how did the SQS service is configured to receive the file details after uploading to s3 bucket in this video https youtu be XZggsCITQdY

I have been watching the video on aws lambda (https://youtu.be/XZggsCITQdY). This video shows configuring the services to send email to an ID whenever a file is uploaded to an s3 bucket on a website/domain. And when a reply is sent by this email id, it will move the file. For this, s3 bucket, route 53, lambda function and SQS service. Here, SQS service is used to give the file details to lambda function as it is stateless. When a file is uploaded to s3 bucket, it triggers the lambda function and also sends the info to SQS.

My doubt is how the SQS / S3 bucket is configured to receive/send file information.