This is a very common confusion because Microsoft uses similar branding for both products! Here’s a clear breakdown:

1. Microsoft Outlook with Microsoft 365 Business

What is it?
A business productivity subscription suite (formerly called Office 365) that gives you:

Web-based and desktop versions of Outlook, Word, Excel, PowerPoint, Teams, OneDrive, SharePoint, etc.
Regular feature updates and cloud integration.
Enterprise-grade security, admin controls, and collaboration tools.

What does “with Outlook” mean?
Outlook is the email client (app for email, calendar, contacts, tasks).
With Microsoft 365 Business, you get Outlook as:

Web app: outlook.office.com
Desktop app: Included in the installable suite for Windows/Mac
Mobile app: iOS/Android
Exchange Online mailbox (business-grade email, calendar, contacts)

Key points:

Always up to date (subscription includes latest versions)
Cloud-first: Tight integration with OneDrive, Teams, SharePoint, etc.
Multiple users: Managed via Microsoft 365 admin center.
License: Pay-per-user, monthly or yearly.

2. Microsoft Office (Standalone Office 2021 or older)

What is it?
A one-time-purchase software suite installed on your PC/Mac:

Includes Outlook, Word, Excel, PowerPoint, etc.
No cloud services (unless using add-ons/free Microsoft account features).
You pay once, use forever (but NO major updates/upgrades).

What about Outlook here?
Outlook is also included as the desktop app only (no Exchange mailbox—must connect to your own mail server or IMAP/POP service).

Key points:

Buy once, use forever (no ongoing updates)
No web apps or mobile apps included (except with limited, free personal Microsoft accounts)
No Teams/SharePoint/OneDrive for Business
No enterprise admin/management controls
No cloud mailbox—email must be provided by your own server/provider

Direct Feature Comparison

| Feature | Microsoft 365 Business | Office 2021/Standalone |
| ------------------------------------- | ------------------------------------------------- | ------------------------------ |
| Pricing | Subscription (monthly/yearly) | One-time purchase |
| Apps included | Outlook, Word, Excel, etc. (web, desktop, mobile) | Desktop only |
| Email hosting | Yes (Exchange Online mailbox) | No (must use your own) |
| Cloud storage | Yes (OneDrive for Business) | No |
| Collaboration (Teams, SharePoint) | Yes | No |
| Updates | Included, always latest | Security only, no new features |
| Admin controls (business) | Yes | No |
| Licensing | User-based, managed in cloud | Per device |

When to Choose Which?

Microsoft 365 Business
Choose if you want cloud mail (Exchange), web/mobile/desktop access, full collaboration, regular updates, and business management features.
Office (Standalone)
Choose only if you want the desktop apps and already have your own email hosting, and don’t care about cloud or collaboration.

Summary Table

| | Microsoft 365 Business | Office Standalone (2021, 2019, etc.) |
| ------------------------ | ---------------------- | ------------------------------------ |
| Email hosting | ✅ (Exchange Online) | ❌ (Need external provider) |
| Web access | ✅ | ❌ |
| Mobile access | ✅ | ❌ |
| Desktop apps | ✅ | ✅ |
| Cloud storage | ✅ | ❌ |
| Teams, SharePoint | ✅ | ❌ |
| Security updates | ✅ | ✅ |
| Feature updates | ✅ (always latest) | ❌ (frozen) |
| Admin tools | ✅ | ❌ |
| Pay once or subscription | Subscription | One-time |

TL;DR:
Microsoft 365 Business = Modern, cloud-based, all-in-one suite with Outlook, email hosting, and collaboration.
Office (Standalone) = Just the installable software (Outlook included, but no mail hosting or cloud features).

If you tell me your scenario (just desktop, or need cloud/collab/email), I’ll recommend the best option for your use case!