It could be confusing to compare the two as SNS does utilize a queue internally.
The main difference is that SNS cares mostly to “push the messages out”, while SQS focus on “letting user pull messages”.
SNS is designed to push messages to multiple recipients. It cares about message delivery, but not consumption. It is more like a dispatcher.
SQS is designed to be able to store messages and let user pull the messages, consume them and then delete upon request. It is more like a cache.