ELI5 Fusion - what is nuclear fusion and why is it important?

What is nuclear fusion and how is it significant to us? How is it different to nuclear fission? What is the significance of the recent news that we have reached ‘ignition’ of nuclear fusion? ... we explain like I'm five Thank you to the r/explainlikeimfive community and in particular the following users whose questions and comments formed the basis of this discussion: wickinked, straight-faced_solo, km89, aetius476, nerdofnight and hurricanebrain To the ELI5 community that has supported us so far, thanks for all your feedback and comments. Send us an e-mail: [email protected]