In Yacapaca, a course is basically a way to collate quizzes into a logical structure. It enables you to provide teachers’ notes and downloadable files such as lesson plans or worksheets. A course also has its own markbook, enabling teachers to see results grouped separately from other assignments should they wish to.
What it’s not: a Yacapaca “course” is a completely different concept from something you would also find called a “course” in Moodle. Can’t really blame them for using the same name, but it hasn’t half caused a lot of confusion.