Looking at Wikipedia (https://en.wikipedia.org/wiki/NATS_Messaging) I see that I'm technically right, it's JetStream that does the storage layer - but it's part of the NATS server.
From memory, I really liked the philosophy of NATS but found the nomenclature confusing.
I have used it mostly for message-first services, and found subject-based messaging a breath of fresh air to decouple services. You can do the same thing with RabbitMQ topic exchanges, but it requires quite a bit more hand-waving.
So you can for example ask for [the first/the last/all] of the messages on a particular subject, or on a hierarchy of subjects by using wildcards. All the filtering is done at the server level.