A simple Turing machine can compute anything any other computer ever could.
Turing imagined a long tape divided into boxes, where a simple machine reads a symbol, decides what to do using fixed rules, then moves left or right. However simple it looks, this Turing machine can, in theory, run any program that today's most powerful supercomputer can run.
Think of a washing machine. It has a fixed program: wash, rinse, spin. A Turing machine, however, can execute any program. It does nothing on its own. It simply follows simple instructions, step by step. This is the secret. Any complex calculation can be broken down into elementary operations. From a video game to a weather forecast, everything reduces to the same basic moves on an imaginary tape. The next step is to understand how such a simple machine can be as powerful as any other computer.
Why it matters His idea laid the theoretical foundation for every computer and phone in use today.