Each of these tend to increase free testosterone levels, albeit by different mechanisms.
Cycling is an all-together different matter, but certainly no less important.
Cycling refers to the strategy of intermittent utilization of hormone therapies. That is rest periods are spaced periodically in the enhancement schedule. With actual hormone replacements a negative feed back loop occurs which tends to diminish endogenous production and down regulate endogenous sensitivity. Releasers, precursors and secretagogues all have the potential of overwhelming the enzyme, co-enzyme and substrate complexes of the related hormones production systems. Cycling helps prevent this upregulation from taking place.