One of the defining features of the RSMembership! component is the possibility to offer users that purchase a subscription on your site extra content. This content will only be available when the subscription is active, once a subscription expires, the bonus content will no longer be accessible until the user renews his subscription.
The most common restriction applied through the component is the content article restriction. With this you can prevent users from viewing the full article if they do not have a proper subscription. The article intro can still be viewed in general listings, the actual restriction is applied only on the article's details page.