A foreign worker is someone who comes from another country to work in a different country. Let's say, for example, that you live in the United States and someone from another country comes to work here. That person is a foreign worker.
Sometimes, people go to work in another country because they can't find a job where they live, or because they want to earn more money. Sometimes, they come to work because they have a special skill that is needed in another country, like being a doctor or an engineer.
When a foreign worker comes to a new country, they might have trouble understanding the language or figuring out how things work. They might miss their family and friends back home. But they also have a chance to explore a new place and meet new people.
Foreign workers are important to many countries because they often work in jobs that people in that country don't want to do, like cleaning or farm work. They also bring different ideas and cultures with them, which can make a country a more interesting and diverse place to live.