If you use Microsoft Word (or a similar word processor), you probably know well enough how to save a document. You click Save, choose a folder, give the document a name, and then click Save, OK, or whatever.
What you may not know is how to choose a different format for that document, or why you'd want to.
By default, Microsoft Word uses its own, proprietary document format. In the old days, that was the Doc format, but as of Word 2007 (and continuining with Word 2010), it's Docx.
Other word processors have their own standards as well. OpenOffice Writer, for example, uses the OpenDocument, or ODF, format. Kingsoft Writer uses a format called WPS. And so on.
Fortunately, these and other programs can save documents in multiple formats, thereby making them easier to access in, well, other programs. That's why, in Microsoft Word, if you click the Save as type pull-down in the Save dialog, you'll see a wealth of choices. Below I've identified some of the more popular ones, and in what circumstances you might use them.
Rich Text Format RTF might best be described as a "universal word-processing format," as it's supported by just about every word processor. However, unlike plain text, it retains basic formatting information, like font sizes and styles.
PDF Adobe's Portable Document Format also has universal appeal, as it can be opened using any number of viewers (including, most commonly, Adobe Reader). You'd use PDF to produce your document in a read-only format, meaning it couldn't easily be edited. It's also a good way to distribute documents online, as most browsers can view PDFs without the need to download them fist.
Plain Text Just like it sounds, this format saves only the raw text--no formatting, no hidden codes, just your words. You might use this to export text that needs to be imported into another program, like a blog tool or text editor--something that won't like all of Word's underlying extras.
Word 97-2003 Document So you've got Word 2010, but your parents are still plugging along with Word 97. The latter can't open documents created by the former (not without a converter, anyway), but at least Word lets you save files using the older formats. Some kinds of formatting may get lost in translation, but this should work for most kinds of documents.
Word can also save files as Web pages, XML documents, templates, and more. Needless to say, if you need to learn about those formats, a little Google searching should reveal all.
Contributing Editor Rick Broida writes about business and consumer technology. Ask for help with your PC hassles at email@example.com, or try the treasure trove of helpful folks in the PC World Community Forums. Sign up to have the Hassle-Free PC newsletter e-mailed to you each week.