(BSC programming tutorial) I don't know how to the other classes where created

I don’t understand how the other classes were created, I have done exactly the same thing on the video but I can’t get to display my balance. I am guessing it has to do with the other classes that were created (see attached image), Please can someone help

This is from an older tutorial which used an older version of the server. These classes won’t be created now, you can read about it here.