Office365? Microsoft365? Microsoft Office 2021? Difference between Microsoft 365 and Office 2021

The branding Office 365 was introduced in 2010 to refer to a subscription-based software as a service platform for the corporate market.
Office 365 is a cloud services platform that offers familiar Microsoft products like Word, Excel, PowerPoint, and OneDrive (along with other productivity services) either online or on-premises via a subscription plan.
In July 2017, Microsoft introduced a second brand of subscription services for the enterprise market known as Microsoft 365, combining Office 365 with Windows 10 Enterprise volume licenses and other cloud-based security and device management products.
Microsoft officially announced that Office 365 was renamed to Microsoft 365 on April 2020.
The new naming convention reflects Microsoft’s strategy of providing a single complete productivity platform for its customers.
It is a subscription service that makes sure you always have the modern productivity tools from Microsoft. Instead of purchasing a one-time license, you pay a recurring fee to access the suite of productivity tools.
Apps and Services: With Microsoft 365, you get access to Office applications (such as Word, Excel and more), 1TB of storage in OneDrive, and minutes for calling phones from Skype.
Plans: There are Microsoft 365 plans for home and personal use, as well as for small and midsized businesses, large enterprises, schools, and non-profits.
World-Class Security: Microsoft 365 includes world-class security features to protect your data and privacy.