For what purpose this extension is used?

Keeps customers updated about the latest offerings and even about price drops.

Do customer have to subscribe for all products or specific products?

Customer can subscribe for specific or all products without any hassle.

Does it allow Guest customer to subscribe for the updates?

Guests customer can register with their name and email address to subscribe to updates

Can admin user change the content of the email for subscriber?

Yes admin user can change the content according to the requirement

Do the admin user needs any technical knowledge to manage the subscriber and the related things to extension?

We have developed the extension in such a way that any person with little or no knowledge of Magento can manage it.