ACH stands for Automated Clearing House. This system is used to make bank transfers from your US checking account to another US checking account. ACH shouldn’t be confused with Bank Wire that works differently and imposes certain fees unlike ACH.
If you want to transfer money to online casinos, ACH processing system enables casino to withdraw money from your bank account after your verification and permission.
Most online casinos don’t have any charges or fees for ACH transactions and most financial institutions and banks don't have it either.