As you can see, this question has been asked and answered before within the last three days. The same ideas that I wrote in the last answer still apply. The biggest difference that I see is that preschool truly focuses on the skills needed for school while infants and toddlers focus on exploring the world around them and practice basic skills such as rolling over, sitting up, walking, smiling, reaching and grabbing a specific item, and moving with a purpose. Preschool focuses on what school skills they will need such as waiting your turn, raising your hand, playing cooperatively and listening with intent and purpose. The true difference is the skills which are either discovered or taught to enable success.
Below is the answer the first time it was asked.
Caring for infants and toddlers is different than a program for preschool aged children. Infants and toddlers are learning the basic skills of living such as how to get food when you want it, how to sit up, how to learn from watching others, and how to walk and talk. These skills require encouragement and opportunity rather than the teaching of skills. Preschool children require more direct, purposeful teaching. They must learn school skills such as sitting still, paying attention, being quiet when needed, working on art projects, and how to work with others. The aim is different and therefore, the ways to help the children learn what is needed are different.