Pages is a document editor for formatted text that provides a Mac alternative to Word. It features iOS integration and generally greater compatibility with Mac OS than many word processing alternatives. It is not available for any non-Apple platform, and saves in its own .pages file format, although exporting to other formats is certainly possible.
One of the things I like about Pages is that, by default, it makes paragraph symbols visible when selected. This should appeal to anyone who's fed up with trying to figure out when they have a carriage return selected or not. However, in the Apple way, this and other additions of user-friendliness are balanced by a lack of some features that power users may find deal-breaking. There also appears to be some basic inconsistencies in the way formatting works in Pages and in Word, which may cause problems in converted documents. I heartily recommend Pages for exporting PDFs though, since it preserves formatting with more fidelity than Word.
Sam's Protip: Pages uses the new saving system introduced in the latest versions of Mac OS. Because of this, one needs to save a copy (duplicate) prior to editing rather than after editing in order to preserve the original in a separate file.