All three of these terms deal with behavioral expectations, which means that all are very fluid in their content within any given society and that they will vary with difffering cultures.
Norms are probably the most rigid or structured of the three. Norms set out "the behaviour that is expected or acceptable in particular circumstances." As such, norms might suggest appropriate clothing for given occasions or locations, for example; in some instances, norms may carry the force of precedent or law. Norms may be passed on through observation and imitation or through direct provision of information.
Mores are closely related to norms but focus more upon the values being demonstrated or refuted through the behavior being followed. Mores could be considered to range from
including moral codes and notions of justice down to strict taboos, behavior that is unthinkable within the society in question
Folkways are the most casual of these three types of expectations. Folkways are usually learned as a result of observation and imitation; enforcement is relaxed and low-key.