The Tree of Jesse refers to a passage in Isaiah that describes the Messiah as a Branch of the tree of Jesse, who was one of the ancesters of jesus Christ.
Isaiah 11:
1And there shall come forth a rod out of the stem of Jesse, and a Branch shall grow out of his roots:
2And the spirit of the LORD shall rest upon him, the spirit of wisdom and understanding, the spirit of counsel and might, the spirit of knowledge and of the fear of the LORD;
The Jesse Tree is used pictorially in Christian art, to represent Jesus genealogical background.