In Cambodia, people speak a language called Khmer. Sometimes, people also speak other languages, like French.
French is a language that comes from a country called France. A long, long time ago, France came to Cambodia and made it their colony. That means they took control of the country and made the people there do things their way.
When France was in charge, they made people learn French so they could communicate with them. They also taught French in schools and used it in government and business. So, many people in Cambodia learned to speak French during that time.
Today, even though Cambodia is no longer a colony of France, some people still speak French. It's like a special language that they know in addition to their own language, Khmer. Some use it at work or in school, or just for fun.
So, in short, French is a language that was introduced to Cambodia when France was in charge, and some people still speak it today as a second language.