When the absolute URL option is on & you add the exact URL condition, we check everything & go for an exact match & then display the notification or captured the data from the form.

Absolute URL means the same page URL but considers uniquely if you enable this option.

Let's understand this by example so you can get the exact idea.

You have one website page mydomain.com/pageurl 

This page you can be accessed through www.mydomain.com/pageurl or http://mydomain.com/pageurl  or http://mydomain.com/pageurl?utm_source=FBads&utm_medium=BannerAds

Absolute URL means All URLs are different which have Http or https, www or without, UTM params. 

Once you enable the Absolute URL option, You are informing us that consider these all  URLs as unique & go for the exact match & perform the task like display the notification or capture the URL.

Relative URLs mean we consider all the above URLs are the same.

By default, We keep Absolute URL OFF ( recommended ). It means without bothering about URL with HTTP or https, UTM params, www or without, query string.  Just consider added URL as  Relative URLs & display the notification & capture the data.

1. In the Display tab: 

2. In the data-source tab