SNS is typically used for applications that need realtime notifications, while SQS is more suited for message processing use cases. SNS does not persist messages - it delivers them to subscribers that are present, and then deletes them. In comparison, SQS can persist messages (from 1 minute to 14 days).

https://ably.com/topic/aws-sns-vs-sqs#:~:text=SNS%20is%20typically%20used%20for,1%20minute%20to%2014%20days).