Subscribe is an option offered by product vendors or service providers that allows customers to gain access to products or services. Most subscription-based models are paid services, which require a customer to pay a subscription fee to access and use a particular product or service.
In addition, many websites, product and services companies, etc., allow customers to subscribe to their newsletters, product/service-related blogs, press releases, etc. In order to subscribe, the customer has to add his/her email address to the company's mailing list. This means that the customer is subscribed to anything sent to that mailing list.
Techopedia explains Subscribe
Often, a subscription requires registration of an email address on a website. The registered email address is added to a repository of customer email IDs, which are used for mass mailing some kind of digital content. Getting daily/weekly updates, coupons or offers from different organizations is also another perk of subscription-based models.
Software as a Service (SaaS) providers also offer a subscription-based model, which includes two types:
Monthly subscription model: In this model, the customers pay on a monthly basis, often through credit cards or automated e-payments. In general, customers are allowed to cancel the subscription any time, with no penalty or fee. Although unusual, a few monthly subscription companies do provide quarterly and annual subscriptions.
Term subscription model: In this model, the customers subscribe to the services for a mutually agreed time period. The subscription agreement might or might not incorporate terms for cancellation during the agreement period. Term subscription models feature flexible payment terms, which may include monthly, quarterly, yearly or a mutually agreed customized payment terms.
In addition to SaaS providers, many websites also use subscription-based models. Some of the popular subscription website types are:
Membership subscription website: Paid members can subscribe to a library of data on a certain topic of interest or a group of topics.
Magazine subscription website: Paid members can subscribe to a digital magazine or a related print or issue of the magazine.
Application subscription website: Paid members can subscribe to gain access to specific online software programs or applications that let them input data, search a proprietary database, access results, etc.
Blog subscription website: A mostly free subscription model where readers can access publisher as well as user-generated content, which is updated consistently and frequently.