A preoperational child has more understanding than a sensorimotor child does. They can easily remember what they see other do even in their absence. They try to do what they saw other do though they do not know whether it is right or not.
For instance, at this level a child will use water to clean their toys but will not have any idea why they use water and not paraffin. They will use it from the experience from others who they see them cleaning using water.