A placement is an optional tool for grouping ad units. It's a collection of one or more ad units where an advertiser's ad can be displayed. You can create placements to identify ad units that an advertiser might want to target.
For example, you operate a news site. You might create one placement that includes ad units for all section homepages on your site. You might create another placement that includes all ad units on pages containing content about sports. Both of these placements could include the ad unit for the front page of the sports section. Other placements might include combinations of ad units appearing in the world news, travel, and weather sections of your site. (Keep in mind that putting the same ad unit in multiple placements can lead to some reporting complexities, discussed below.)
Ad units in multiple placements
If you share an ad unit across multiple placements, all placements that contain that ad unit will show up in order and line item reports if any one of the placements is targeted. This can make reporting harder to reconcile, but it might be the most convenient way to organize your inventory.
How it works in detail
- Placement "Animals" contains ad unit "Puppy" and ad unit "Cow".
- Placement "Pets" contains ad unit "Puppy" and ad unit "Kitten".
Line item 1 targets placement "Animals", but not placement "Pets".
When you run a report on line item 1, in addition to placement "Animals" being included because it's targeted, placement "Pets" will also be included because it shares ad unit "Puppy" with placement "Animals.
While the data for each placement is still technically correct, you'll be unable to reconcile reporting numbers because one ad unit's metrics can be attributed to multiple placements.