Like humans , plants produce a variety of hormones that help regulate their internal functions.
Five major classes have been identified.
Auxins: promote stem elongation and root growth
Cytokinins: promote cell division
Gibberellins: promote stem elongation and flowering
Ethylene: promote fruit ripening
Abscisic Acid: inhibits cell growth during times of stress Hormones are synthesized in one part of the plant and typically transferred to another part of the plant.
So, for example, auxins created in the apical (dominant) bud are often trans-located to the outer root zone to promote root growth or to lower stem locations to inhibit lateral buds.
As you can see, changes made to one location of the plant can impact development in other locations, e.g., topping your dominant bud removes auxin development capacity which may allow more lateral bud development.