All Microsoft Word documents contain styles – even if you haven't applied one. New blank Word documents are based on Normal template, and text you type uses Normal style. One way of seeing what styles are in your document is to expose Style Area Pane in Draft and Outline views.
"In Word 2010, go to File tab, click Options, and click Advanced. Under Display, set width of the Style area pane width in Draft and Outline views to 1 inch or so. Click OK. Now when you go to Draft or Outline view, you'll see the style for each paragraph shown in the column to the left of your text. To remove Style area pane, grab vertical black line with your cursor and drag it to the left. If all the paragraphs in your document show as the Normal style, your Word doc and your work flow mayn't be all it can be," explainded Microsoft.
Watch the video for a quick overview on how to apply styles in Word 2010: