These could be written as swappings: (AE) (BD) (CG) (FH) in the first case and (AE) (BF) (CG) (DH) in the second.
There was a practical advantage to this Enigma property.
It meant that the deciphering operation was identical with the enciphering operation.
(In group-theory terms, the cipher was self-inverse).
The receiver of the message had only to set up the machine in exactly the same way as the sender, and feed in the cipher-text, to recover the plain-text.
There was no need to incorporate 'encipher' and 'decipher' modes into the Enigma machine, which made its operation that much less liable to mistakes and confusion.
But it was associated with a grave weakness, in that the substitutions thus performed were always of this very special kind, with the particular feature that no letter could ever be enciphered into itself.
This was the basic structure of the Enigma.
But there was much more to the machine actually in military use.
For one thing, the three rotors were not fixed in place, but could be removed and replaced in any order.
Until late 1938 there was a stock of just three rotors, which therefore allowed a total of six arrangements.
In this way, the machine offered 6 × 17576 = 105456 different alphabetic substitutions.