If you have multiple ads in an item, so you can control that they appear in a certain order, but follows booked impression number
Standard, follows planned impressions
Focused mostly on zones, and if you have multiple Items, where it tries to deliver the right ad to the right page with best CTR is.
Delivers over time, ie allocates exactly how much it will deliver a day during a booked period
If you have a package product, the delivery is better distributed between the spaces in the product.