Unlike subscriptions for print magazines where you keep each issue, subscriptions for new cloud software such as Microsoft 365 evaporate once the time period passes. In that sense, these new productivity terms are more like monthly cable subscriptions.
While you no longer have the program to use if your subscription lapses, you do keep all documents you created within it.
The office suite subscriber typically pays a monthly or yearly fee in return for access to the software, which is a product, but one housed on a remote server rather than one's own desktop.
Microsoft Office Suite, Subscription-Style
For some time now, Microsoft has been following a subscription model with Office 365, its cloud service product, but this has not included full versions of Microsoft Office--just apps for Word, Excel, PowerPoint, Outlook, and OneNote.
Office 365 subscriptions (excepting the free version) will now be integrated with not just pared-down Office Web Apps, but full cloud versions of Office 2013 programs. You will now be able to choose either option.
Pricing for Office 2013 (both subscription and desktop versions, as well as information on upgrades)
Microsoft is not necessarily the trend-setter of subscription office suites, but since it is still the world's productivity powerhouse, the newly-integrated Office 2013 subscriptions have users asking a lot of questions.
Microsoft has a number of reasons a subscription to Office 2013 could increase your productivity, including staying up-to-date with productivity features. The latest version of Office will be continuously made available to you, rather than needing to update.
Subscriptions require a smaller investment up front, since you pay as go.
Also, since subscriptions are housed in the cloud, you can potentially access programs and files from more devices, in a uniform experience.
Alternative Office Software Suites Using Subscription Models
Subscription plans have added complexity to office suite purchasing, but that complexity does yield more options--hopefully ones of benefit to you. As ever, please let me know if you have any questions.