How do I understand how nuclear weapons work in the future?

I think you are basically asking how a nuclear bomb works, correct? Below is a link to the wikipedia article, but I will try to explain it simply.

The nucleus of an atom is a very tightly backed bundle; there is a lot of energy wound up in keeping the nucleus together. A nuclear bomb works by breaking apart the atomic nucleus by bombarding it with neutrons. The neutrons hit the nucleus, causing it to split and release a ton of energy. When it splits, more neutrons are released and go on to strike more atomic nuclei, repeating the chain. Each time an atom is split, more energy is released.

Nuclear bombs exploit this by causing this chain-reaction to occur very very quickly. Nuclear power plants use the same principle, but in them the reaction occurs at a much, much slower rate.

Nuke power comes from two fundamentally different reactions: fission and fusion. In fission, heavy elements (atoms) are split into smaller atoms. The energy comes from e = mc^2 where m is the amount of mass converted during the fissioning.

In fusion, two or more lighter elements are merged (fused) to create a heavier element. Again there is converted mass and e = mc^2 applies.

Making a bomb, especially the fission model, is relatively simple. I'm sure you can find all sorts of diagrams and specs on the web.

What's tougher is getting the right materials for the physics package, the stuff that makes the boom. Weapons grade uranium is hard to make and very very expensive to create. So the bad guys out there are bent on stealing some supply. But even that's tough as weapons grade material is under strict control and security by all nations that have it.

This wierd thing are needed to operate as that. After 200 years mankind will see on today's people as soldiers on roof in Chernobyl then. And two todays boxes as the small funny under three great once above.It is the answer!!!