Interview Question | Software Engineer | What if your customer is not technically good and you have to explain what an API is?

You must know that the question is not to judge your knowledge about API. The interviewer here wants to know how good you are at explaining complex and technical things to a layman. 

The ideal answer must contain the definition of API in the language of a commoner. You can say:

“It is a very generic part of all programming cases such as websites, mobile applications, desktop applications etc. It basically helps to use a piece of software in another piece of software.”

Additionally you can add some examples such as how it works when you post something to facebook or twitter etc. Basically your answer must cover what it is, what it does and why it is needed.