RE = RegionalExpress and are covered by Interrail/Eurail :)
S-Bahn = Usually marked with the Line S(x) X= a number between 1-85 is covered because operated by German Rail :)
U-Bahn = Usually marked with the Line U(y( Y= a number between 1-55 is not covered because it´s operated by Public Transport of Berlin BVG :)

Please note to use S-Bahn and Regionaltrains within Berlin you need a active Travelday :/

Other option is to buy a cheap dayticket for Berlin Public transport this Covers U-Bahn,S-Bahn,Tram,Buses, Ferry and Regionaltrain within the choosen Validity Room :)

For Berlin itself Berlin AB is enough for rides arround Berlin like Potsdam or our new Airport you would need a ABC ticket :)

Thanks again Seewulf.