v0 is Vercel’s AI tool. You describe in one sentence what you want to build and get a finished web interface back: React code with Tailwind CSS, next to a preview you can try out right away.
What I find interesting is the design mode. Instead of writing another prompt, you click an element and change spacing, colour or font size directly in the result. You can also set up your own design systems, meaning colours, typography and styles that apply across all your projects. That is the point where a tool like this becomes genuinely useful for designers.