When you insert a citation into a Word document, the citation is embedded in field codes, such as:

Field codes hold reference information for your formatted citations, and are typically hidden.
To hide field codes in Word:
Word 2007, 2010, 2013:
In Word, click the Microsoft Office button in the top left corner.
Click the Word Options button.
Click Advanced.
Scroll to the "Show document content" section and clear the box titled "Show field codes instead of their values."
Click OK.
Note: An easy way to turn field codes on or off is to press Alt+F9.
In Word, go to the Word menu and select Preferences.
On the View menu, clear the box titled "Field Codes."
Click OK.
Your citations will now appear correct in the document. Field codes are still there, and are necessary, but they are hidden from view.