Your questions totally make sense after you say your going to be barely turning 16. Just going out on a limb right away here just from what this site is majorly for, don't even think about doing a cycle yet. If you were or weren't just wanted to get that out of the way. As for strength training goes, I believe your just wondering about strength vs hypertrophy.
I was under the impression that training for size focused on creating muscle damage and training for strength focused on improving the central nervous system.
Muscle hypertrophy is the result of the repair process set in motion after the stress of lifting loads causes micro tears in the muscle fiber. The degree to which damage occurs is influenced by several factors including load, but mostly time under tension. Longer times under moderate loads creates the most damage.
In any muscle contraction only the minimum number of fibers required to move the given load are recruited and used. Strength training attempts to improve the central nervous system's ability to recruit more muscle fibers to perform a given lift. Maximal loading is required to give the CNS more practice. Fewer reps and sets are required to avoid fatigue and over-training. I assumed that when more fibers were recruited less muscle fiber damage occurred, yielding strength improvement without size gains.
I'm not an expert so fire away.