The scrambling action of the Enigma rotors are shown for two consecutive letters. Current is passed into the set of rotors, into and back out of the reflector, and out through the rotors again. The greyed-out lines are some other possible paths within each rotor; these are hard-wired from one side of each rotor to the other. Letter A encrypts differently with consecutive key presses, first to G, and then to C. This is because the right hand rotor has stepped, sending the signal on a completely different route; eventually other rotors will also step with a key press.
Own work based on: Enigma-action.png by Jeanot
Enigma-action.svg: MesserWoland / derivative work: Warrakkk