They are explosives, but they aren't used as 'bombs' per se—they do destroy things but they're only intended to destroy projectiles that would otherwise hit whatever they're protecting. When placed on the armored side of something, say a MBT(Tank) the armor pushes back against the blast of the explosive charge and forces all of the energy outwards to repel/destroy an incoming projectile.

Without sufficient armor to deflect the blast however, it becomes detrimental rather than helpful—it might punch a hole in the side of your APC, and in theory it would be even worse for people since there's nothing at all in between the explosives and the vital fleshy bits that keep us alive.