All schools across India are affiliated by one body and other the most common both that are there are either individual state boards or CBSE that is the Central Board of Secondary Education. CBSE is responsible for issuing out a syllabus for each class and each subject taught in that class. syllabus is something that every student is provided with from the beginning of their academic life. Syllabus is a list of content of everything that a particular subject aims at teaching the students and expecting them to learn it. 
The syllabus is an important part from the very beginning meaning from the junior-most section of the school to class 12. The reason why syllabus plays such an important part is that it is not simply just a list of all the topics and subtopics are covered in a subject in a particular class but instead, it is also what makes the students understand exactly what is expected out of them in a particular class. It makes it clear for them to only focus on what is included in the syllabus. As students move to higher classes they tend to opt for coaching classes which sometimes confuse them with the subject matter or the syllabus. Coaching classes teach from a perspective of preparation for external competitive exams that take place outside the school and not the CBSE board exams. This results in them teaching the students even what is not included in the syllabus. The syllabus is also sometimes taken lightly by the school teachers along with the students, what is being taught in the coaching classes is what students will leave would be asked in their school examination. This is a huge mistake that students make. As the syllabus for those external exams and the syllabus for CBSE board exams are sometimes completely different. This ends up in students losing marks in important school examination and spoiling their overall results for a particular academic year. In order to not make these mistakes students should make sure to refer to their syllabus before beginning the academic year and also in between before each examination and before starting to prepare for the examination. In short, it is important that the students thoroughly know their syllabus and understand what exactly is expected out of them. The best and the most convenient way of keeping the syllabus handy is by using Extramarks as it is a site that provides syllabus for cbse board exam on its website that the students can access whenever and wherever needed.
https://www.extramarks.com/syllabus/cbse