Student or Learner
what do we mean by ; trhe right of working full time?
First you need to know what the word "right" means in this context. It means
something one is allowed to do. So if you have the right of working full time you are allowed to work full time. From your previous threads here at UsingEnglish, I reckon maybe you are talking about some specific laws in your country. Maybe you want to say that children do not have the right to work full time, because they are prohibited by law, since they must have time to study.
Working full time is when you have a complete day work (let us say morning and afternoon, or let us say about 8 hours a day). It is the opposite of working part time, when you work only for half that period.