This story is about love and about what people do for the ones that they love.
In the story, Jim and Delia have very little money. But they want to buy each other Christmas presents. So Jim sells his dearest possession (a watch) to buy combs for Delia's hair. Delia's prize possession is her long hair. So she has it cut and sold to buy a nice chain for Jim's watch.
So what has happened is that they have each sacrificed their most prized thing for the other. This, the author is saying, is true love.
The story is pretty short, you could easily read it in 20 minutes. It feels set in the early 1900s and their poor state does indeed cause them to each risk their most prized possession for each other. The irony of the story though is that the gifts purchased are now meaningless because what Jim bought Della was for her hair(which is now gone). Della bought Jim a chain for a watch(which he sold).
Although the message is about great sacrifice, it keeps you wondering because the sacrifices made lost their value once given as gifts. Does this mean material objects are of less value? Yes. Does it mean what is on the inside matters more? Yes.
The story "The Gift of the Magi" is a tale about giving so totally of oneself that one sacrifices that which is most important to one so that another person can be happy. In the story a man and his wife have very little other than a place to sleep, food, and one another.
The wife is proud of the beauty of her long hair. Her husband has a watch piece that he had inherited that means everything to him. To make each other happy they both sacrifice what they have that is most important to them. He sells his watch to buy her combs for her beautiful hair. She sells her hair to buy a band for his watch.
In the end the two have the gifts from one another but the tangible items mean nothing as they do not have the hair to wear the combs or the watch to attach to the band. However, they have the greatest gift of all. "They both have the gift of the sacrifice made by one another out of love for each other."
The title "The Gift of the Magi" relates this sacrificial gift subtly to the birth of the Christ child. It was the Magi that came to give the child gifts when the child is actually the gift to the Magi and all mankind.