Campaigns can be designed on a pay-per-view, click, or conversion model. Google ads are typically set up in pay-per-conversion or pay-per-click mode, while Facebook ads typically follow pay-per-view mode.

As a rule of thumb and just for illustrating purpose1: on an pay per click campaign, one GBP equals one click. This means that google will show you add every time a client searches your keywords and charge you only if the client clicks the add.

1 This example illustrates the cost per click model and the relation one GBP equals one click is valid an approximation that would vary based on the demand of the specific keyword. Furthermore, not every person that will search for the keyword is a client. This is why it is very important to design a targeted campaign that avoid extra-costs derived for poorly configured ads.