What is differentiation and redifferentiation?

Answer:

Differentiation: the process by which cells derived from meristems (apical and lateral) undergo structural and functional changes to become mature, specialised permanent cells, e.g. formation of tracheary elements that lose their protoplasm and develop lignified walls.

Redifferentiation: the process by which dedifferentiated cells (permanent cells that had regained the power of division) divide and their products again lose the capacity to divide and mature to perform specific functions, e.g. formation of secondary xylem and phloem from interfascicular cambium and of cork from cork cambium.