Answer:
A nuclear weapon is currently the largest explosive device that a nation may use as a weapon. There are basically two different kinds, and they include the fission devices, and the fusion devices. There are a lot more fission weapons around than fusion weapons. And in the fusion weapon, because extreme heat is required to initiate fusion (of hydrogen into helium), a "regular" fission device must be set off either "around" or "up against" components to initiate the fusion event. The fusion device (the so-called hydrogen bomb) is arguably the larger of the two as regards destructive power. It makes a really, really big blast.