Generally, when running an ad such as a banner or pay-per-click ad, marketers will add URL parameters to their links that identify key features such as the campaign's type, content, and source. So if your campaign "ad_campaign=123" needed to be identified, you could put that "ad_campaign=123" into a URL parameter to track leads that interacted with that specific ad.
You can also leverage these URL parameters inside of RTP to show campaigns tailored and targeted towards these specific leads.
Targeting the Leads
To identify these leads, you would create a Segment using the Include Pages filter and searching for this specific URL parameter within the URL.
For example, if you had an ad with a link to "http://www.yourpage.com/page.html?ad_campaign=123" you could use the following Include Pages filter to target your campaign to those leads.
Be sure to include asterisks before and after the parameter - these wildcards will allow you specify the parameter value inside the URL rather than the exact URL itself.