(For more details, see “ What are the differences between Microsoft Office 2019 and Office 365?”)
When you purchase a perpetual version of the suite - say, Office 2016 or Office 2019 - its applications will never get new features, whereas Office 365 apps are continually updated with new features.
Microsoft sells Office under two models: Individuals and businesses can pay for the software license up front and own it forever (what the company calls the “perpetual” version of the suite), or they can purchase an Office 365 subscription, which means they have access to the software for only as long as they keep paying the subscription fee. Nearly everyone who uses Office ends up using Word at some point, whether it be for writing memos, typing up agendas, creating reports, crafting business correspondence or any of a thousand other uses. Word has always been the workhorse app of the Microsoft Office suite.