Some guy wanted to know who the 'neighbour' in the Old Testament referred to. Jesus then recounted the story of the good Samaritan. Basically a man from a community despised by Jews who exhibited far better Jewish/Christian behaviour than the two 'respectable' citizens who had passed by earlier.
Basically a man lay injured from having been assaulted by robbers. The 'religious' types ignored his plight but the infidel (the Samatitan) took pity and helped.
Thus your 'neighbour' is the person who shows the most humanitarian response to your suffering.
The problem with the parable is that the Samaritan is merely rewarded with 'Neigbourliness' and is still consigned to hell, despite his good deeds, because he has never had the good fortune to have been raised by Jews or Christians. Meanwhile the religious types who ignored the sufferer's plight probably squeezed into heaven because they knew who to pray to.
A beautiful parable, that sadly seems incomplete.... Come on Jesus, what did become of the good Samaritan? Does he reside with you, or is he damned because he was born on the wrong side of the tracks?