The Marketing Funnel
When creating a campaign, you can choose an objective which reflects the purpose you want to drive traffic for. This will influence the engine's choice of traffic sources and the Cost Per Visit. Objective can either be "Awareness" or "Conversions".
Top Of The Funnel Traffic (Awareness)
The top of the funnel is where everyone goes in (visiting your site). Only the most interested buyers will move further down your funnel. This is where your campaign journey starts , by showing your Ads to people who are interested in your service. Your visitors need to start here in order to move down the funnel.
Bottom of The Funnel Traffic (Conversions)
The bottom of the funnel is the “purchase” stage of the customer journey. It occurs after the visitor is done researching and is soon to be a “new customer.” Visitors are close to purchasing or taking your desired action (i.e.: sales, lead submission, app download, etc)