Placement properties include the cost structure, flighting, and dimensions of placements where your ads appear. They help you identify, plan, and schedule your placements. Most placement properties are for reporting purposes only.
For example, when you run a report on ads in your placement, the report only covers the start/end dates you set in your placement properties. However, a few placement properties affect things beyond reporting, such as payment source, tag types, ad blocking, and dimensions.