You can use Display Planner to:
see how other advertisers perform on websites where you want your ad to appear
compare how your current Display Network campaign could perform on websites you’d like to target
see ways to reach your target audience based on your keywords, website, or interest categories
see which image and text ads are performing best on the specific websites you’re targeting
see which images and text ads within your campaign are performing best on the specific websites you are targeting
run a report to determine which keywords are most likely to convert based on the past 30-days of your campaign
see potential webpages where your ad can appear based on your keywords
managed CPC bids for contextual campaigns within your account
You can use Display Planner to
Display Planner generates ideas for all the ways you can target the Display Network. Targeting ideas are based on your customers’ interests or your landing page. They include keywords, placements (websites, videos, mobile apps, mobile app categories), topics, interests (affinities, in-market segments), demographics (age, gender), and remarketing.
Display Planner shows you the potential reach and cost of targeting ideas to help you plan your Display Network campaigns.You enter keywords, topics, or websites that you think are likely to match your customer interests, and your landing page. That will get Display Planner started with the types of targeting and keywords that can build the foundation of your campaign.
Read more here: https://support.google.com/adwords/answer/3056115?hl=en
Display Planner shows you the potential reach and cost of targeting ideas to help you plan your Display Network campaigns. The forecasts can help you understand how your ad groups could perform and historical costs can guide you to the ideas that are within your budget.
You can save your plan directly to your AdWords account as a new campaign or as an addition to an existing campaign or ad group. You also have the option to download your plan to review or update at a late time.
This article describes the basic features of Display Planner, including targeting ideas, placement ideas, and forecasting.
Before you begin
If you haven’t used Display Planner before, read About Display Planner first.
You can find Display Planner at the top of your AdWords account, under Tools. When you first open Display Planner, you’ll have a choice of four options to start building your campaign. In each section, you’ll enter your campaign language and location targeting, bid type, and ad format filters.