I am going to have to assume you are referring Alan Turing's Bombe, a machine he used to aid in the decryption of the Enigma code.

The machine itself, to put it very simply, is a collection of rolling cylinders and wires, and its only purpose is to roll through all the possible combinations of the Enigma's encryption settings, and stop when there are no contradictions in the message. In other words, it simply sped up an otherwise very tedious process.

To be very nitpicky, the primary hard work behind cracking the code was human analysis using mathematics and logic, and a healthy dose of operator error from the Enigma operators. The machines at the time were simply there to reduce the menial labour. Without the machines, women would be recruited to do the menial calculations instead.