Are nuclear 'fusion' and nuclear 'fission' the same thing? Is one safer (to humans, the environment, etc.) than the other?

Nuclear fission splits heavy atoms like uranium to release energy. It's used in today's power plants but creates long-lasting radioactive waste and carries meltdown risks.

Nuclear fusion joins light atoms like hydrogen to produce even more energy. It's what powers the Sun and stars. Fusion is much cleaner, safer, and doesn't produce dangerous waste, but it's still experimental and not yet ready for everyday use.

Bottom line:
Fission is practical but risky.
Fusion is promising and safe, but still futuristic.

https://www.iaea.org/topics/energy/fusion/faqs