What is the difference between admanager.AdManagerInterstitialAd and interstitial.InterstitialAd

Earlier I was used com.google.android.gms.ads.doubleclick.PublisherInterstitialAd in my app. From the google documents it says com.google.android.gms.ads.admanager.AdManagerInterstitialAd is the new class to be used instead of the previous one. We have com.google.android.gms.ads.interstitial.InterstitialAd also. I would like to know the difference between these if any? Can I use any of them instead of the com.google.android.gms.ads.doubleclick.PublisherInterstitialAd

If you use Google's ad services like AdSense or AdMob Google will both provide the ad from their supply of ads and deliver the ad using their technology. DoubleClick for Publishers is a service that lets publishers use Google's ad delivery technology to deliver ads without Google providing the ad. This lets publishers sell ads themselves and still use Google's technology to display these ads.

• InterstitialAd is the Admob version where Google will provide the ad for you.

• PublisherInterstitialAd is the version where you sell the ad space
  yourself and then you use google's technology to display it.

Google Ad Manager is an ad management platform for large publishers who have significant direct sales. Ad Manager provides granular controls and supports multiple ad exchanges and networks, including AdSense, Ad Exchange, third-party networks, and third-party exchanges.

Use Ad Manager if you need:

• A central place to monetize all of your inventory types (websites, mobile apps, videos, or games)
• To manage a significant amount of ad revenue that comes through direct deals from buyers
• To use third-party networks to compete for ad inventory More complex reports to gain granular insights

More info here.