General English is for everyday conversation and includes a variety of subjects like everyday life, travel, sports, food.
Business English includes how to conduct meetings, attend exhibitions, write emails, write formal letters, get ready for a presentation... as well as any business language adapted to students' business situation.
Specialist subjects depends on the student's needs and wishes and tutor's capacity. This includes research on the tutor's part on the subject the student is interested in. This includes but is not limited to subject such as law, medical, automotive, thesis...
For example, a law student might need help with courses in English. In this case, the student can provide the teacher with the law texts so that the teacher may study them and help them with the course.