Hyphens were a lot more common in the days of the typewriter. They cropped up more frequently then because sometimes you'd start typing a line near the right margin and realize too late that it wasn't going to fit. So, you'd hyphenate the word, in a way that made sense, you hoped, and move on. (Kids out there, ask your parents about typewriters.) Today, when words simply wrap to the next line, we're content to leave large chunks of space along the right margin. But sometimes this space doesn't look so hot, and hyphenation could be in order.
The beauty of hyphens in Word is that they are removed automatically if you edit your text later and the word moves to another line. So, you don't have to go back through your document looking for improperly hyphenated words. To hyphenate a long word manually, click where you want the hyphen to appear and press Ctrl-Hyphen (the key with the symbol you would normally use to hyphenate). As long as the word breaks, the hyphen will appear. If a shift in spacing joins the word, the hyphen vanishes.