Xylem and phloem are the two main transport tissues in plants, and they perform different functions.
The xylem carries water and minerals from the roots up to the leaves. Its transport is one-way, always upward. Most of the cells in the xylem are dead at maturity, which helps form strong, hollow tubes. The main types of xylem cells are tracheids, vessel elements, fibers, and parenchyma. The xylem also gives strength and support to the plant because its cell walls are thick and reinforced with lignin.
The phloem, on the other hand, carries food made in the leaves to all parts of the plant. Its transport is two-way, meaning it can move up and down depending on where food is needed. The cells of the phloem are living, including sieve tubes and companion cells. Phloem also has thin walls and helps in storing and distributing nutrients.
In short, xylem moves water and minerals upward and provides support, while phloem moves food throughout the plant.