What makes a placement a "managed placement" is that you’ve chosen to target a website, mobile app, or ad unit specifically. In practice, this means adding the placement to the ad groups in your Display Network campaigns, similar to the way you’d add keywords.

The basics

• A placement has to be part of the Display Network for your ads to show there.
• If a specific website you target has an equivalent app, your ads can also show there. 
• You can only add managed placements to certain campaign types: "Display Network only," "Search Network with Display Select," and "Video."
• As with all Google Ads, you'll compete with other advertisers to show your ads on placements you select.
• If you choose popular sites or are just getting started with advertising on the Display Network, you may need higher bids to get impressions. You can always adjust your bids later.

Why add managed placements

Show your ads only on specific placements you choose

If you want to run ads on the Display Network but only on placements you’ve hand-picked, you can do so with managed placements. For example, if you sell travel packages and want your ads to appear on a particular website or a specific page about travel, add it as a managed placement.

Show your ads on placements where your customers spend time

If you know of a website that your customers visit, consider adding it as a managed placement. For example, if your typical customer spends a lot of time on example.com and you want your ads to appear there, add it as a managed placement.

Get more (or less) traffic from placements by setting individual placement bids

If you find that advertising on a specific site works well, you may decide to increase your bid for just that one site to be more competitive and increase your potential exposure on that site. On the other hand, you may want to reduce your bid for another placement that may not provide as many conversions.

* Nguồn: Google