Overlap targeting allows you to create more complex relationships between the different attributes you wish to target. Overlap targeting is available on Custom Audience, Interest and Behaviour targeting.
The easiest way to understand overlap targeting is to see an example. Let's say we're a company trying to sell a particular fashion accessory, we might begin our interest targeting this way:
The results of targeting these interests creates an audience of 53,000,000. Essentially, there is an 'OR' in between each interest. With overlap targeting we exchange the 'OR' for an 'AND', like this:
The result can be illustrated this way:
Overlap Targeting Audiences