The TLDR is that Webb can see much further across the universe (and thus much further back in time) and at higher higher resolution than Hubble, and Webb’s primarily Infrared sensors can see through nebulae, space dust and other obstructions better. There are numerous videos on the differences, but here are some I found pretty good:
2. NASA scientist reviewing Webb’s Carina Nebula image, explaining what Webb is unveiling for the first time, and comparing to the same image from Hubble: https://youtu.be/3y6iWi95ypc&t=2m17s
1. Scientific American comparing how far back in time Webb can see vs Hubble: https://youtu.be/nBDHqquK_8k&t=2m8s
2. NASA scientist reviewing Webb’s Carina Nebula image, explaining what Webb is unveiling for the first time, and comparing to the same image from Hubble: https://youtu.be/3y6iWi95ypc&t=2m17s
3. Good overview of Webb and its differences from Hubble: https://youtu.be/JzDWpvtDJ9g