If you take a course through CDLI then your class will likely include students from other schools besides yours. A typical class size is about the same as you might expect to find in any school. The difference with CDLI is that the students may be from anywhere in the province. Your course will have a live ('synchronous') component in which you interact, in real time, with your instructor and your classmates. The class will also include an asynchronous component which will provide you with time to complete assigned work, labs etc., but without direct contact with your teacher.
Despite the fact that the course is 'offered online,' a CDLI course is the same as one you could take face to face. It includes the same curriculum outcomes and uses the same amount of class time. Depending on your own learning style, you should find the course no different from what you have come to expect. CDLI courses work well with your regular course schedule. For example, on any given day you may find yourself working with your on-site classmates and taking a course face-to-face in one period and then working with off-site classmates working on a CDLI course in another period. This may even happen from year to year. For example, you may take a level 2 Science course face to face this year and then take the corresponding level 3 course by CDLI the following year, or vice versa.
To you, this will be seamless. You will attend school and do the program that is right for you. Some of it will be done locally and some of it will be done through CDLI. In the end you will receive one transcript with all of your courses combined, regardless of how they were taken. In fact, your transcript will list your school as the school you graduated from and not CDLI.