API
also Application Programming Interface
A defined way for two pieces of software to talk to each other and exchange data or trigger actions.
Analogy
Like a telephone line between two apps so they can request things from each other.
Why it matters
Every integration you build in n8n, Make, GHL, or code ultimately calls an API, so it's the backbone of automation.
In practice
Your app calls the Anthropic API to get a reply from Claude.