Explain the term Protoderm?

The protoderm is one of the so-called "primary tissues" because it is formed first during germination and subsequent plant growth. The protoderm grows on the surface of the root, and matures into the epidermis of the plant body, providing for protection, as well as absorption of water and nutrients. The epidermis consists of a single layer of cells that cover the interior tissues of the root. Epidermal cells near the root tip protrude outward to form projections called root hairs, which actually carry out most of the absorption from the soil.