Both are systems of measurement. In the metric system, to convert a bigger unit to the next smallest unit, you divide by 10. To covert a smaller unit to the next bigger unit, you multiply by ten. This makes it very easy to use and accounts for its popularity.

The metric system originated in France after the French Revolution, and today has been adopted worldwide as an international standard. Even the few countries that still use the imperial system have adopted the metric system for most industrial and scientific purposes.

The imperial system originated in England, and spread throughout the countries in the British Empire, many of which now belong to the British Commonwealth. It's not the same system used in the United States, although it's similar. That's because the imperial system was not standardized until an Act of Parliament in 1824. So there are some differences between the American system and the imperial system.

The imperial system contains a lot of historical quirks that make it harder to use than the metric system. But it has been used for so long that it survives in many places.