What is the magical realism? Explain how “A very old man with enormous wings” by Gabriel García Márquez is an example of such a story?

I'm going to give you the GradeSaver explanation only because it is excellent. I'll hook you up with the source-link at the end.

"Very Old Man" is perhaps the clearest and most famous example of a genre that Garcia Marquez helped to create: magical realism. This style, simply put, combines elements of ordinary life with elements of fantasy and magic. One might say that a work of magical realism treats the magical as ordinary - and thus invites us to consider the ordinary as magical. Despite containing similarities to folk legends and fairy tales, stories adhereing to "magic realism" avoid the naive moral judgments found in those folk genres. Instead, magical realism creates a complex and problematic world free of moral lessons or any maxims. "Very Old Man" can hence be read on many levels. On first read, it can be deceptively simple: a tale of a town dealing with a lost angel. It sounds like a children's story, which is precisely what Marquez called it. Indeed, Marquez relies heavily on the myths and legends of rural South America and draws from such folk-sources' naivite and simple style. But rather than use these folk elements in a straight-forward manner, Marquez concentrates on their openness to interpretation. The story calls into question the manner in which humans make sense of their world - through stories, tales, interpretations, conversations, conventions, etc. So, in the vain of magic realism, the old man flying away at the end can be seen as something of a cautionary tale rather than a magical fantasy.