ChatGPT reached 100 million users faster than any app in history. It can write emails, explain concepts, debug code, translate languages, and brainstorm ideas. The free version uses GPT-3.5. ChatGPT Plus ($20/month) adds GPT-4, DALL-E image generation, web browsing, and custom GPTs. It's the Swiss Army knife of AI tools — start here if you're new.
**Key takeaway:** ChatGPT is the default starting point for AI beginners.