A legend is a story, with important ontological consequences, passed by person to person.
A legend is a concept, an ideal or semi-true story with mythic qualities usually involving an heroic character or fantastic place and rooted in a kernel of truth; it is a meme that propagates through a culture.
Some legends we know today have their basis in historical fact. Before the invention of the printing press storytellers abounded, and typically would learn their stock in trade, their stories, from an older story teller, who might (or might not) have actually been there when the "story" was "history" bardic schools, oral history.
Examples:conspiracy and conspiracy theories in that the lynchpin of the latter two is usually a plausible, but unprovable secret agenda which exclusively drives the story.
Legend is also the name of a 1984 fantasy novel by David Gemmell, his first novel featuring his character Druss the Legend.