What's the difference between Microsoft 365 and Office 365?

The naming has gotten messy. Here's the cleanest way to think about it:

Office 365 (the original brand)

The cloud-based Office apps and services: Word, Excel, PowerPoint, Outlook, OneNote, Teams, OneDrive, SharePoint, Exchange Online. Microsoft has been migrating away from this brand — "Office 365" SKUs were renamed to "Microsoft 365" in 2020 for most plans.

Microsoft 365 (the current brand)

Office 365 PLUS additional components depending on the plan:

• Windows 11 Enterprise licensing (E3, E5)
• Intune device management
• Microsoft Defender (for Office, for Endpoint)
• Entra ID (Azure AD) Premium plans
• Microsoft Purview (compliance and information governance)
• Power Platform components

The plans that still exist

Microsoft kept "Apps for" naming for the standalone Office apps without other services:

• Microsoft 365 Apps for Business / Enterprise — just the installable Office apps, no Exchange/Teams/SharePoint
• Microsoft 365 Business Basic — cloud-only Office, Exchange, Teams, SharePoint
• Microsoft 365 Business Standard — everything in Basic plus installed Office
• Microsoft 365 Business Premium — Standard plus security stack (Defender, Intune, Entra ID P1)
• Microsoft 365 E3, E5 — enterprise plans with unlimited users and expanded compliance/security

Practical advice

For most SMBs, the right plan is Microsoft 365 Business Premium ($22/user/month). The security stack it includes (Defender, Intune, Conditional Access via Entra ID P1) usually pays for itself versus buying these separately. Once over 300 users, you graduate to E3 or E5.