Explanation:

They extend horizontally from the primary root (radicle) and serve to anchor the plant securely into the soil.
This branching of roots also contributes to water uptake, and facilitates the extraction of nutrients required for the growth and development of the plant.
Many different factors are involved in the formation of lateral roots. Regulation of root formation is tightly controlled by plant hormones such as auxin, and by the precise control of aspects of the cell cycle.
Such control can be particularly useful: increased auxin levels, which help to promote lateral root development, occur when young leaf primordia form and are able to synthesise the hormone.
This allows coordination of root development with leaf development, enabling a balance between carbon and nitrogen metabolism to be established.