Managed placements allow advertisers to:
- give Google the ability to select placements for them and set industry appropriate bids
- bid differently for specific placements on the Google Display Network
- target relevant placements across the entire GoogleDisplay Network based on their keyword lists
- exclude a specific ad unit on a network page where there are multiple ad units
Explanation: You can use managed placements to assign a unique bid to a specific webpage. If your ad performs well when it shows on a certain webpage, you could add it as a managed placement and set a higher bid.
Read more here: https://support.google.com/adwords/answer/99502