Subscription
The "Subscription" module works in conjunction with your website's restricted area and should therefore be used when you a protected area within your website which you only want to make accessible to users who have purchased a subscription. This restricted area will contain every content (text or downloadable files) that is to be reserved for subscribers.
Specifically, with the "Subscrption" module you can create different types of subscription with their own associated description, price and duration. Visitors will be able to purchase them (paying by credit card or any other method as configured by the site's administrator) and get access to the restricted members' area.