The cortex of any living organism usually refers to its center. The difference between the cortex and the endodermis is the prefix "endo-" refers to inner or inside. These are the cells that are on the inside of the stem and root systems that are unspecialized as of yet. These cells lie between the epidermis, the outer layer of cells and the vascular, or conducting cells, of the stem and root systems of plants. The vascular system in plants consists of the xylem and the phloem, which conduct water and nutrients through the root and stem systems to the upper parts of the plant to help facilitate the process of photosynthesis. The cortex covers all these inner working structures , the endodermis, the epidermis the striated cells, the xylem and the phloem, or the vascular bundles. So the cortex would be a general designation, while the endo derm refers to a specific piece of the cortex.
Endoderm is the inner layer of the cortex, and cortex is the outer portion of stem or root of the plant.
It refer to the root part of the plant