Point to Point means message(s) is sent from one application(producer or sender) to another application(consumer/receiver) via a queue. There can be more than one consumer listening on a queue but only one of them will be get the message. Hence it is Point to Point or One to One.
On the other hand Publish/Subscribe is another messaging model where a message(or publication as it is commonly called) is sent to multiple consumers(or subscribers) through a topic. The topic is the link between publisher and subscriber. The subscribers may or may not acknowledge the published message. Implementations like JMS acknowledge the message the messaging providers but not the sender of the message. Publications will be received by all subscribers, durable and non-durable. Any new subscribers on the same topic will not get the publication unless it is a Retained publication.
I would recommend you to read further on,
- Durable subscription
- Non-durable subscription
- Retained publication