A unique feature of the IB Diploma is the Core with the three mandatory components - the Extended Essay (EE), Theory of Knowledge (TOK) course, and a programme of extra-curricular experiences called Creativity, Activity, Service (CAS) Programme. This core is compulsory and central to the philosophy of the Diploma Programme.
The Extended Essay is independent research into a topic chosen from one the student's subjects and under the guidance of a supervisor (a teacher in the school). This is an excellent preparation for tertiary education and promotes high-level research and writing skills, intellectual discovery and creativity.
TOK is a course which stimulates critical thinking and aims to connect the IB subjects and the Core elements. TOK supports the Diploma Programme subjects through common reference and shared goals.
IB is not just about taking exams but is also based on the goal of maturing and developing other parts of the student’s life. CAS is part of the IB Core where students take part in extra-curricular activites outside school. These must cover all three aspects of the CAS course i.e. Creativity, Activity and Service to the Community.
Source: IB TOK Guide 2015