When you type a normal hyphen in Microsoft Word, it can be "broken" meaning that the words on the left and right sides of the hyphen can be placed on separate lines with the hyphen being the last character on a line. Most people think this looks kinda bad. If you want to keep this from happening, you can use non-breaking hyphens instead. A non-breaking hyphen is treated as part of the word and this ensures that the entire hyphenated word is always on the same line.

To type a non-breaking hyphen, hold down the the Control and Shift keys when you type a hyphen.

Of course all these extra key strokes can be hard to remember. So what I do instead is I just type normal hyphens and then when I'm done with my document I go convert all of the hyphens into non-breaking hyphens at one time. You can perform this conversion by doing a Find & Replace (from the Edit menu select Replace...).

Once the Find & Replace dialog is shown, enter - as the thing to find and enter ^~ as the replacement text. Yes, that's a carat and a tilda, not a typo. This will get converted into a non-breaking hyphen when the replacement occurs.