If you had to describe an API to someone completely new to the industry with little to no technical background how would you describe it.
-Where does it exist?
-How does it work?
-How does it securely process CC transactions?
-Is it a piece of software or is it code?
-How does it arrange the transaction information from the shopping cart?
I would describe an API as the vocabulary with which you can interact with a program or service, the information which it expects, the form in which it expects it, and what you can expect to receive back from the program.