In Celtic mythology, Tír na nÓg ("Land of the Young") is used to describe a portion of the Otherworld -- a supernatural realm of "everlasting youth, beauty, health, abundance and joy."
Also in Celtic mythology, ravens are often associated with "darkness and death – especially the death of warriors in battle."
That's all the background you need to appreciate this short from Fursy Teyssier, a French animator, director, cover illustrator, "songwriter, singer, and multi-instrumentalist musician," who made the short in memory of his grandparents.
Actually, you probably don't need any background. It's wonderfully clear.