There is no single global standard for electrical systems. Each country developed its own plug types and voltage levels independently during the early adoption of electricity.
Why plug shapes differ
Different countries created their own plug designs based on safety standards and engineering decisions at the time.
Why voltage differs
Some countries use 110–120V systems, while others use 220–240V. Higher voltage is more efficient, while lower voltage was historically considered safer.
What this means for travelers
You may need a plug adapter, a voltage converter, or both depending on your destination and device.