Manifest function is something, which can be noticed easily. Latent function is deeper and not all the participants are aware of it. Whereas manifest function is known by all participants of the social institutions.
For example, if a criminal is punished, everyone knows that it is the society’s way of saying that deviance of behaviour is not permitted in society. This is manifest function. But the latent function of this punishment upholds the society’s faith in its collective conscience.
Social scientists need to know beyond the common sense perception of the participants and observe the latent consequences of social structures.