Click to run, CTR, Office 365, Office on Demand. What does it all MEAN?

Office 2013, Office 2013, Click-To-Run (aka CTR), Office 365, Office on Demand, MSI installers ... it seems like there are dozens of ways to buy (or rent!) Microsoft Office (including PowerPoint), but it's hard to figure out what you get with each, or how to compare them. We'll try to shed some light on that here.

First, what's it CALLED?

Office versions have names (Office XP, Office 2010) and they have numbers (Office 9, 10 ... 14, 15). Sometimes you'll see this new version of Office called Office 2013, sometimes Office 15.

We'll call it Office 2013 here.

As to all the different ways you can buy, rent, install and use Office 2013 ... read on.

Click-To-Run or CTR

Click-To-Run isn't a specific product, it's a relatively new way of installing Office on your computer. It "streams" installation files down from the internet as they're needed and sets itself up in a kind of virtual machine.

It was introduced in Office 2010, where it was Not Good. But Microsoft must have been watching it very closely, because the Office 2013 Click-To-Run installation has corrected many, if not all, of the issues that came up in Office 2010 CTR. Some of the improvements in Office 2013 CTR:

It no longer sets up a fake Q or other-lettered drive on your computer.
It's no longer so isolated that it breaks add-in installers or anything else that depends on registry settings.

CTR has a few advantages over the type of installers (called MSI installers) that we're used to from installation CDs/DVDs:

Because it's virtualized, it doesn't interfere with your existing Office installation. You can run CTR and your previous version of Office side-by-side, without them getting into catfights.
In theory, it should be able to update itself on-the-fly, downloading new files as Microsoft makes them available. It remains to be seen whether MS makes this a practical reality.

And a few disadvantages and/or claimed advantages that don't seem to work out as well as MS might have hoped:

It wants a solid, fast internet connection for the installation, and for any features that download later, as you make use of them. No connection? Sorry, no feature.
Even with a reasonably fast connection, some users have found that installations are slow; on a DSL line, several attempts at CTR installation took well over an hour each.
Microsoft says that because the installation streams, you can immediately begin using the software as other needed files download in the background. This is, at best, wildly optimistic, unless by "use the software" you mean "watch a splash screen flashing marketing messages at you". To be fair, this is based on the early Preview versions of Office 2013 CTR, and other users reported that it installed quite quickly for them. In other words, the jury is still out.
You have no installation media. No CD, no DVD, not even a downloaded SETUP.EXE or other installation file. What if you need to re-install and you don't have a good internet connection or don't have much time to waste? With a CTR installation, you're out of luck.

All in all, we figure that as long as Microsoft continues to make a good old-fashioned disk/file-based installer available, seriously consider getting it rather than using the CTR option. Unfortunately, they don't. Unless you purchase a volume license, you get Click to Run.

MSI

MSI means MS Installer (or something along those lines). It's the kind of installer that Microsoft has been shipping on CDs and DVDs for the last umpteen years. It's proven, reliable technology that pretty much solves all the problems raised by CTR installers.

Which do I have?

Most likely, you have CTR, but to be sure:

Click the File tab then click Account then look at the options under Office on the right.
If you see Office Updates with an Update Options button next to it, just above About PowerPoint, you have a Click to Run version.
If you see only About PowerPoint (but nothing about updates), you have an MSI version.

Incidentally, you might want to turn updates OFF before you start a presentation; otherwise, updates might install and force a reboot, right in the middle of your big show. Very unprofessional.

Office On Demand

Office On Demand is an Office licensing approach that uses technology similar to CTR. It installs a temporary copy of an individual Office application on any Windows 7 or newer PC you want to use; a friend's computer, library computer, a borrowed or rented PC, etc. When you're done using it, it disappears from the computer. Like CTR, it requires internet access, but as long as you have internet access, you can run Office, which is pretty cool.

Office Web Apps

Microsoft Office Web Apps are web-based versions of the main Office programs (PowerPoint, Word, Excel, etc.) There are several implementations of Web Apps:

One available via a free SkyDrive account (see SkyDrive section below)
One available through Office 365 subscriptions (see Office 365 section below)

These web apps have very limited functionality compared to the full versions you're used to on your desktop/laptop PC, but once you store your documents on SkyDrive you (and others you give access to) can view and/or edit them from pretty much any internet-connected computer, PC, Mac or even some smartphones and tablets, and all without having to install anything.

The PowerPoint web app is also an excellent way to display presentations to people who may not have PowerPoint or a compatible viewer installed on their computer.

The exact features offered by the SkyDrive vs Office 365 web apps will differ and may change over time as Microsoft updates them and makes them more capable. Because they're hosted on web servers rather than on your computer or other device, you get the benefit of any improvements immediately, without having to do anything at your end.

Also pretty cool: The web apps also work on Mac computers and some mobile devices (phones, tablets, etc).

SkyDrive

SkyDrive is a free cloud-based (ie, web-based) Microsoft service that gives you a big chunk of free storage on the internet.

New users get 7 GB of storage
Microsoft provides an additional 20 GB if you buy Office
Long-time SkyDrive users who've kept their accounts active get 25 GB

You also get synchronization features and access to the web-app versions of the popular Office programs.
Sign into SkyDrive here if you already have an account
Learn more about SkyDrive here

Note: due to a naming conflict with the products of another company, Microsoft has agreed to drop the "SkyDrive" name. As yet, we haven't heard what the new name will be.

Office 365

Office 365 is a subscription-based version of Office. You pay for it by the month. The cost depends on the level you choose (ie, the features you need). There are various Office 365 plans, including:

A $4/month plan that includes basic web-based email, calendars and directory synchronization, but no Office apps at all.
A $6/month plan that adds instant messaging, the web-app versions of Office, a team site for sharing files, a public website.
A $20/month enterprise plan that includes all of the above and more, plus desktop rather than web-app versions of the Office apps (for up to 5 devices per user)
Other plans that offer various levels of Office document viewing vs. viewing + editing. Read the terms very carefully!

Compare the Office 365 subscription plans here.

Compare the regular (MSI and CTR) versions of Office 2013 with Office 365 here

Here's further information about Office 365, including links for getting started setting it up.

Summary

Click-To-Run (CTR) and MSI are installation technologies, methods for installing Office, not specific versions of Office.
Office On Demand is a subscription service that lets you temporarily install needed Office apps on any compatible, internet-connected computer you're using at the moment.
Office Web Apps are web-based versions of Office apps that let you view Office documents online and, to a limited extent, edit them.
Office 365 is a way of purchasing Office by monthly subscription rather than outright. Different subscription levels offer different feature sets at different prices.

Or if you'd rather hear it from the Microsoft mouth:

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