Endosperm is a nutritive tissue in a seed which develops before the development of an embryo. It contains starchy carbohydrates as food reserves which are required for the growth of the developing embryo. In case of cereals like wheat, maize, rice, etc. the endosperm is not completely consumed by the developing embryo and remains persistent. 

When it comes to human consumption, the wheat can be categoried as whole wheat and refined wheat.

The whole wheat contains an outer part called 'bran' which is nutritious for human consumption as it contains variety of nutrients and dietary fibres (which increases the faecal bulk and help to reduce the time taken by food to travel from the mouth to the anus of the alimentary canal).

While the refined wheat lacks bran and thus the part of the seed which is consumed by humans is the endosperm containing only starch (which is a complex carbohydrate). Thus it is not that nutritious for human consumption.

But for the growth of the embryo, the endosperm is necessary as the starch stored in it is broken down to release energy which is consumed by the embryo for its growth.