What is an API? An active SE explains the meaning of 'API integration' with diagrams

For those who watched the story about the 'restaurant server' on my Reel, this is the continuation.The API episode is one of ...

What are AI tool 'API keys' and 'usage fees'? Calculating monthly costs with examples

When reading descriptions of tools that use AI, there are terms that often appear: 'You must use your own API key' and 'API ...