What are lateral roots?

Hint: Root is the descending part of a plant growing inside the soil. It is mainly divided into tap root and adventitious root, in which the taproot main root gives rise to thin root branches which are also known as secondary root or tertiary root, it helps to increase the surface area for absorption of water and minerals from the soil.

Complete answer:
The root of a plant constitutes a descending axis that grows inside the soil. There are generally two types of root systems present, taproot system, and adventitious root system. The taproot develops from the radicle of an embryo and forms primary root which later gives rise to secondary roots which are also known as lateral roots which further form tertiary roots and rootlets. Adventitious roots are developed from any part of plants other than radicals and branches. The root consists of parenchyma cells in the vascular cylinder of the pericycle and the parenchymatous cell of the pericycle gives rise to new lateral meristems and these lateral meristems from lateral roots. The lateral roots are considered as endogenous in origin because it initiates from pericycle and grows out through the cortex and epidermis. Lateral roots help to increase the surface area for absorption of water and minerals from the soil, it also provides anchorage and increases the volume of soil.

Note:
In the case of woody roots, lateral meristems form secondary phloem and secondary xylem initiated from the pericycle region. The number of lateral roots depends on its initiation center and the number of lateral roots can be calculated by using colchicine which is a cell division inhibitor.