In biology, the term "vessel" can refer to different structures depending on the context. Here are the different types of vessels and their functions:

• Blood vessels: These are the branching tube-like structures that carry blood throughout the body. There are three main types of blood vessels: arteries, veins, and capillaries. Arteries carry blood away from the heart, veins carry blood from body tissues back to the heart, and capillaries are tiny vessels that enable the actual exchange of water and chemicals between the blood and the tissues. Blood vessels deliver oxygen and nutrients to the organs and tissues in the body and carry waste products and carbon dioxide away from them.

• Vessel elements: These are one of the cell types found in xylem, the water-conducting tissue of plants. Vessel elements are found in angiosperms (flowering plants) and form an efficient system for transporting water (including necessary minerals) from the root to the leaves and other parts of the plant.

In summary, "vessel" in biology can refer to blood vessels or vessel elements in plants.