Office 365 is a subscription service that ensures you always have the most up-to-date modern productivity tools from Microsoft. There are Office 365 plans for home and personal use, as well as for small and midsized businesses, large enterprises, schools, and non-profits.
All Office 365 plans for business include the robust Office desktop apps that you’re familiar with, like Word, PowerPoint, and Excel. You also get extra online storage and cloud-connected features that let you collaborate on files in real time. With a subscription, you'll always have the latest features, fixes, and security updates along with ongoing tech support at no extra cost. You can choose to pay for your subscription on a monthly or yearly basis, and the Office 365 Home plan lets you share your subscription with your family for up to 6 people, and use your apps on multiple PCs, Macs, tablets, and phones.
Most of the Office 365 plans for business, schools, and non-profits include the fully installed desktop apps, but Microsoft also offers basic plans with the online versions of Office, file storage, and email. You decide what works best for you: Small business, Enterprise, School, or Non-profit.
Office 2019/2016/2013 is sold as a one-time purchase, which means you pay a single, up-front cost to get Office apps for one computer. One-time purchases are available for both PCs and Macs. However, there are no upgrade options which means if you plan to upgrade to the next major release, you'll have to buy it at full price.
Office Online is a free version of Office that you can use in a web browser. All you need is to sign up for a Microsoft Account with a new or existing email address. Try the Office Online apps.
Not sure what you have now? See What version of Office am I using?