The Centimeter corresponds to one hundredth part of the meter. The length is a magnitude created to measure the distance between two points, the units most used to measure the length are kilometer, hectometer, decameter, meter, decimeter, centimeter and millimeter. If you do not have a ruler at hand and you need to estimate the length of something in centimeters, use a pencil or pen, for example. Because the thickness of these objects is usually one centimeter.
The Inch is still today, widely used by anglophone nations. The inch originated in the ancient age, where the Romans measured some lengths with the own thumb. As this measure was not exact and depended on the size of the thumb of the average person, it ended up creating immense problems. For this reason, from 1959, a correspondence between the inch and the meter was established. Even in countries that have adopted the metric system, television, computer monitors, smartphones and tablets are still often expressed with diagonal measurements in inches.