a subscription sells periodic (monthly or yearly or seasonal) use or access to a product or service, or, in the case of such non-profit organizations as opera companies or symphony orchestras, it sells tickets to the entire run of five to fifteen scheduled performances for an entire season. Thus, a one-time sale of a product can become a recurring sale and can build brand loyalty. It is used for anything where a user is tracked in both a subscribed and unsubscribed status.