How we change what others think, feel, believe and do
Fantasy stories are typically set in medieval civilizations and are characterized by the presence of magic.
The characters are often sharply divided into good and bad, with few uncertain or neutral characters in between.
Fantasy stories may well include classic structures, such as Campbell's 'Hero's Journey' Monomyth. Thus there may be magical weapons, monsters to fight and great forces of good and evil.
J.R.R. Tolkein's Lord of the Rings is the archetypal
Fantasy stories are often preferred by technophobes who do not like science fiction, and idealists who hark back to 'simpler' days and the clear differentiation between good and back.
Fantasy stories often take place in other worlds. It is also popular to have parallel worlds, with 'real world' people crossing over into fantasy lands.
Magic can be used by authors to 'cheat' their way out of difficult situations. In some ways, fantasy stories use magic to compensate for the lack of science as a device for taming nature.
Change stories can use fantasy as an analogy for the real world, with things cast in black and white and magic being used to resolve the irresolvable.