Microsoft offer Microsoft Accounts, Office 365 Personal, Office 365 Home, and Office 365 for Business to cover the following services / products (among many others):
Email
Data storage and synchronization
VoIP (Voice over IP)
Microsoft Office
I've been working closely with most of these systems for years and I can honestly say that each generally works quite well but Microsoft seem to be doing their absolute best to confuse everyone and to blur these completely separate products together.
Let's take a closer look.
Microsoft Account
A Microsoft Account can be created for free and it can be managed via https://account.live.com/. I have listed the details of what it provides and how in this context below:
| Service / Product | Provided by | Accessed via |
|---|---|---|
| Outlook.com | https://mail.live.com/, Apps | |
| Data storage and synchronization | OneDrive | https://onedrive.live.com/, Apps |
| VoIP | Skype | http://www.skype.com/en/, Apps |
| Microsoft Office | Office Online | https://office.live.com/ |
Simple so far, right? Okay, let's move on then...
Office 365 Personal and Office 365 Home
An Office 365 Personal or Office 365 Home subscription can be bought and must be assigned to a Microsoft Account and it can be managed via https://stores.office.com/. I have listed the details of what it provides and how in this context below:
| Service / Product | Provided by | Accessed via | Extra benefits |
|---|---|---|---|
| Data storage and synchronization | OneDrive | https://onedrive.live.com/, Apps | 1TB of storage |
| VoIP | Skype | http://www.skype.com/en/, Apps | 60 monthly minutes |
| Microsoft Office | Office.com | https://office.live.com/, Apps | Always up-to-date apps |
So, this is just a paid version of a Microsoft Account, right? Correctamundo! On we go...
Office 365 for Business
An Office 365 for Business subscription can be bought and must be redeemed to an Office 365 tenant so that its license can be assigned to a Microsoft Account for Organizations (also known as "a work or school account"). I have listed the details of what it provides and how in this context below:
| Service / Product | Provided By | Accessed via |
|---|---|---|
| User accounts | Azure Active Directory | https://login.microsoftonline.com/ |
| Exchange Online | https://outlook.office365.com/, Apps | |
| Data storage and synchronization | OneDrive for Business | https://domain.sharepoint.com/personal/username_domain/, Apps |
| VoIP | Skype for Business | https://outlook.office365.com/, Apps |
| Microsoft Office | Office Online, Office 365 | https://office.live.com/, Apps |
The confusion
"Well, that all seems relatively straight-forward. Why exactly is this all so confusing?" I hear you saying (I don't really, I just imagine that you're thinking it). Fair enough, the confusion and frustration become apparent when you look closer and you have extensive experience so I have listed examples below:
Office 365 for Business accounts used to be called Organizational Accounts which was simpler to differentiate but are now called Microsoft Accounts for Organizations.
Office 365 volume licenses can be managed via the Volume Licensing Service Center which is accessed via a Microsoft Account.
Office 365 for Business used to be managed via https://portal.microsoftonline.com/ but is now managed via https://portal.office.com/ - the same domain that is used to manage Office 365 Personal and Office 365 Home.
Logging in at https://login.microsoftonline.com/ sometimes inexplicably redirects to https://login.live.com/.
Office 365 ProPlus (Microsoft Office supplied by Office 365 for Business) connects to https://ols.officeapps.live.com/olsc/OlsClient.svc to activate.
Microsoft Accounts used to be called Windows Live IDs hence why a lot of services are hosted on the live.com domain. An example of this is Outlook.com which used to be called Windows Live Hotmail.
As reported by The Verge at http://www.theverge.com/2015/5/5/8552965/microsoft-outlook-com-office-365-migration, "Microsoft's Outlook.com will be powered by Office 365".
Exchange Online's MX records are domain.mail.protection.outlook.com - the same domain that Outlook.com is branded as.
Exchange Online is actually a trimmed-down, slightly different, ever-changing version of Exchange 2013.
OneDrive and OneDrive for Business used to be called SkyDrive and SkyDrive Pro, respectively, but had to change their names due to a dispute with Sky.
OneDrive for Business is the application, not the service. The service is provided by SharePoint Online.
SharePoint Online is actually a trimmed-down, slightly different, ever-changing version of SharePoint 2013.
OneDrive for Business / SharePoint Online has absolutely ridiculous restrictions (see Microsoft's "Restrictions and limitations when you sync SharePoint libraries to your computer through OneDrive for Business" support article at https://support.microsoft.com/en-us/kb/2933738 for full details) including:
A maximum of 5,000 or 20,000 items, depending on the type of library. This can be reached surprisingly easily and, if I recall correctly, screwed up the entire sync process for a client and had to be setup from scratch.
A maximum of 2GB data. Large ZIP or ISO or collection of images? Out of luck.
Unsupported characters of \ / : * ? " < > | # %. Look familiar? Windows restrictions includes unsupported characters of \ / : * ? " < > |. Did you notice that # and % are missing? Yeah, you can create filenames including # and % ("Survey #1.JPG", "20% standard rate tax.XLSX", etc) in Windows but they will NOT play nice with the OneDrive for Business app and, if I recall correctly, screwed up the entire sync process for a client and had to be setup from scratch.
Skype for Business is is actually a not-yet-entirely rebranded version of Lync Online.
Of course, this is only an overview and doesn't include things like Kiosk plans which provide Exchange Online mailboxes that are only accessible via Outlook Web Access.
I hope that this is at least informative to someone.