The concept of sharing really does not develop until around age 3. When your child is a toddler parallel play, or playing near each other rather than with each other, is the norm. Since the sense of sharing does not develop until preschool age, try not to scold or punish toddlers who are not sharing the way you would want. They will not understand why they are being punished. Instead, acknowledge that they are worried about getting their toy back, or that they want to play with it. Try to explain why we need to share our toys or snack.
Language skills are also developing during this time, so not only will your child not understand the concept of sharing, he will not understand the word “share,” either. For this reason it is important to explain when you are demonstrating that good behavior. If you are sharing some food, with him, tell him what you are doing. Similarly, if he offers you something, say, “Thank you for sharing,” so he hears the word again and beginning to understand that you approve of this type of behavior.