system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How can explosives like C4 be so stable?

Basically I'm curious how that little bit of matter can hold all that explosive potential, but you can basically play soccer with it and it won't explode. 

What exactly does trigger it and WHY does that work, when kicking it and stuff does nothing? (I don't need to know exact chemicals or whatever, I'd rather not be put on a list)
gpt
Let's say you have an extinct volcano with a big caldera at the top (a large pit). At the bottom of the pit is a boulder. It will take so much energy to get that boulder up to the edge of the caldera, but once you get it over, the boulder will roll down the entire volcano releasing many times the amount of energy.

This is the same concept for explosives.

Instead of gravity and hills, we are working with bond strength. The bonds in C4 are pretty strong, so random energy from just sitting around is unlikely to break them and even a surprising amount of physical shock. However, if you can put enough focused energy into some of the substance, the atoms become free to bond in a different configuration and when they do, they release more energy than it takes to break them up. Much of this energy goes into breaking up other bonds in the immediate area, those atoms recombine into other molecules, release a bunch of energy, and continue the reaction.

The easiest way to trigger the initial breaking of bonds is to use a primary explosive (e.g. a blasting cap) but an electrical current can also do the trick.