A course is a lesson that does not need be taken by all students in the class(es) allocated, but can be chosen by individual students. Regular lessons of a class are therfeore compulsory lessons for all students of a class, the courses need to be selected by the students explicitly.
In order to convert lessons into courses, the desired lessons must be selected (by highlighting them with the mouse) and then clicking on the <Convert lesson(s) into course(s)> in the toolbar of a lessons view.
In some cases it is easier to just remove individual students from a course than allocating the majority of a class to a course. Therefore converting a lesson into courses always raises the question if all students (of the classes involved) should be allocated to the course. By clicking ‘No’, no students are initially allocated to the course.
A (c) is displayed in the "Cl,Te" column of a lessons view to indicate that a lesson has been converted into a course.
If you want to re-convert courses into regular lessons click on the <Remove from course choice>button.