Word 2013 is Microsoft's latest word processor, part of the Office 2013. It boasts improved performance on the previous version, and more features.
If you didn't like the ribbon interface that was introduced in Office 2007, then you're not going to like Word 2013. The ribbon interface is back but has been improved on. Menu items have been moved around to make the most commonly-used features more easily accessible. The menu items in the ribbon have received aesthetic updates to make them more easily distinguishable from one another.
There is also a 'Touch Mode,' making Word 2013 much more touch-friendly than previous versions. This mode is only available if you have a touch screen enabled computer. Buttons will become bigger, making it easier to select items.
The welcome screen has been redesigned to be more useful. You can see your recently-opened documents as well as a bunch of new templates. There is also a search box at the top where you can search for more templates online. This is extremely handy since Word 2013 doesn't include every type of format out of the box.
Inserting pictures is much easier now as Word 2013 can pull in photos from your Flickr, Facebook, and SkyDrive accounts. Word 2013 also allows you to search for pictures under the Creative Commons license with Bing. There are also new guides to make placing and sizing images much easier within Word 2013.
PDF support is also much improved in Word 2013. PDFs will now open in Word as if they were Word documents. You can convert Word documents to PDF, which will retain the formatting you've done. Converting and opening PDFs in Word 2013 happen quickly.
New for Word 2013 is the ability to download apps. Microsoft has an Office apps store where you can download and install different productivity tools like dictionaries. While some apps are useful, they do take up screen space and don't work well with multiple documents on one screen.
Collaboration has also gotten easier with Word 2013. You can still track changes but if you have an Office 365 account, comments can be synced to everyone's document so everyone collaborating on the document will have access to the most recent version. Comments can be marked as done and will be grayed out, making it less distracting.
If you're happy with your current word processor, there may not be enough new features to make upgrading to Word 2013 compelling. Still, Word 2013 offers incremental updates and features that make it the best version of the word processcor yet.