The main advantage of using real objects in the classroom is to make the learning experience more memorable for the learner. To give a couple of simple examples, if you are going to teach vocabulary of fruit and vegetables it can be much more affective for students if they can touch, smell and see the objects at the same time as hearing the new word. This would appeal to a wider range of learner styles than a simple flashcard picture of the fruit or vegetable.
Hadassah Hall 