Learning objectives determine new knowledge and skills that a learner will gain by the end of the course.
In the new course editor you can add learning objectives to course sections (they are visible only for a course developer, not learners). When a learning objective is defined you can create content/question items that are associated with this learning objective.
If you need help while creating a descriptive and meaningful learning objective you can try our learning objective maker. The link to it appears when you start typing in a learning objective.