It is not encrypted, so, anyone could recover the information from the contents.
But it's signed. So, when you receive a token that you originally issued, you can verify that it actually came from you and has not been tampered with in-transit.
But it's signed. So, when you receive a token that you issued, you can verify that it was you who issued it.
That way, you can create a token with an expiration of, let's say, 1 week. And then when the user comes back the next day with the token, you know that user is still logged in to your system.