You can use Display Planner to:

see ways to reach your target audience based on your keywords, website, or interest categories
compare how your current Display Network campaign could perform on websites you’d like to target
see how other advertisers perform on websites where you want your ad to appear
see which image and text ads are performing best on the specific websites you’re targeting

The correct answer is:

see ways to reach your target audience based on your keywords, website, or interest categories.