Learning objectives, or learning outcomes, define the goals and expectations of a lesson. Learning objectives for individual lessons connect to the broader goals of a unit or course. Not only do learning objectives help you plan your curriculum, they also let students know what they will have learned by the end of a particular lesson.
The key to writing learning objectives is to make them SMART: Specific, Measurable, Attainable, Relevant, and Timely. Your assessment will tell you whether your objective was specific and measurable enough, while the lesson context dictates the objective's attainability, relevance, and timeliness.