From what I understand, it's using an LLM for coding, but taken to an extreme. Like, a regular programmer might use an LLM to help them with something, but they'll read through the code the LLM produces, make sure they understand it, tweak it wherever it's necessary, etc. A vibe coder might not even be a programmer, they just get the LLM to generate some code and they run the code to see if it does what they want. If it doesn't, they talk to the LLM some more and generate some more code. At no point do they actually read through the code and try to understand it. They just run the program and see if it does what they want.