Have you read the story of "Giving Tree"?! it is one of the most simple and touching stories I ever read. It is a children book but reading it you realize how deep it is and how different one can look at the story.The tree character shows someone that is always a giver and he is happy when there is something he can offer. on the other side there is the boy which is always a taker ( although we don't know how he is with others but for sure with the tree he is a taker). Throughout our life we met people that belonged to one of these 2 groups or somewhere in between. The boy can be seen as selfish or very reasonable and the tree can be seen as someone who sacrifice himself for the sake of others or someone that is selfless.
If you had not read the book, here is a short and old video with the voice of Shel Silverstein himself.