Professional services are jobs that often require a lot of education and special skills. Do you know how you go to school to learn how to read and write? Well, some people go to school for a really long time to learn how to do things like be a doctor, a lawyer, or an engineer. These are called professional jobs.
When people do these jobs, they are providing professional services. For example, when you go to the doctor, they are providing you with a professional service by giving you a check-up and helping you feel better.
Similarly, when someone is having trouble with the law, they may hire a lawyer who provides them with a professional service by helping them understand their legal rights and defending them in court.
People who provide professional services often get paid a lot of money because they have gone through a lot of schooling and training to learn all of the special skills needed for their job.