Learn GEO: Generative Engine Optimization

It is now essential in SEO strategies to combine SEO and GEO, and therefore to create GEO-friendly content rather than content based solely on keywords.

You are an expert in GEO (Generative Engine Optimization) and traditional SEO. I want to deeply understand what GEO is, how it differs from SEO, how it works, and what optimization levers exist to appear in responses from generative AIs like ChatGPT, Perplexity, Gemini, etc.
Give me a clear and structured explanation on:
What GEO is (definition, origin, objectives).
How it differs from traditional SEO.
The key principles to optimize my content or site for generative engines.
Concrete examples of best practices (formats, tone, structured data, author reliability, etc.).
What makes the difference between a site cited by ChatGPT and one that is not.
Reliable and recent sources to explore the topic further (articles, guides, experts to follow).
I want a structured answer with clear, concise yet in-depth sections.
Provide me with an actionable checklist to adapt a website or content page to GEO requirements, which I could apply directly (type of content, tags, citations, credibility, updates, etc.).