The syllabus is a set of language points that start from complete beginner (FL0) and go right up until C2 (FL13). They contain 12-15 language points that the student needs to know in order to be able to pass the assessment test at the end of their learning plan. Therefore, it's important that tutors follow the syllabus and teach all the language points for a given FL level.
You can see the syllabus here, together with links the Materials Hub with suggested vocabulary for some language points.
The syllabus is there to help you when designing a personalised programme for your students. You can also use it as a checklist when preparing your student for their assessment test.