What Does Means Subscribe?

Publish/subscribe (or pub/sub) is an asynchronous messaging paradigm
where senders (publishers) of messages are not programmed to send their
messages to specific receivers (subscribers). Rather, published
messages are characterized into classes, without knowledge of what (if
any) subscribers there may be. Subscribers express interest in one or
more classes, and only receive messages that are of interest, without
knowledge of what (if any) publishers there are. This decoupling of publishers and subscribers can allow for greater scalability and a more dynamic network topology.
(Source: en.wikipedia.org )

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