What is the difference between the main root and the lateral and adventitious roots?

The root system of plants is formed by 3 types of roots: main, lateral and adventitious. The main root develops from the root of the seed embryo and is well developed in plants from the Dicotyledonous class. The lateral roots extend from the main root in the conductive zone, which is why it is called the lateral root zone; adventitious or additional ones depart from the shoot.

The root system with a well-developed main root is called the taproot, and the one where the main root is lost among the numerous adventitious ones is called fibrous.