A 'raw' button will get the .button class. It will also look like the 'Primary' button, as that is the default. If you don't add any of the classes mentioned in the following, you can style your button completely to your own liking. The standard colour classes in Foundation are:
These classes also have their own specific hover state colours. If you add the class .hollow, you will get outlined buttons, and with the class .clear only the text will remain, plus the padding.
The class .disabled has no hover state colours for obvious reasons, but you may add it to buttons already having the .hollow or the .clear classes. All the buttons also may have rounded corners or dropdown shadow.
With the classes
you can change the size of the buttons. The size 'normal' obviously comes between small and large, and that is what you get when you don't set any size class.
See the Foundation pages for more tips and ideas.