A false belief which is unexplained by reality and is shared by a number of people is:

There are many beliefs which are false and are shared by whole communities e.g. black magic, witches, etc. These beliefs are considered as superstitions. In comparison, delusions are not shared by members of the same sociocultural background. For example, if a villager stas claiming that he is lord Hanuman, no one in his village will share his beliefs.