How exactly an API works?

An API is like a helper that lets two different apps or systems talk to each other easily. When a person (client) wants something, like data or a service, their request goes to the API. The API takes this request, checks it, and passes it on to the server or database. The server finds the right answer and sends it back to the API, which finally gives the answer to the person. APIs make it simple for different things to work together without needing to know how each one works inside.

Example : Imagine Person A wants to order pizza but doesn't know how the pizza shop makes it. Person B is the delivery guy who takes orders and brings food. Person A tells Person B, "I want one Margherita pizza." Person B passes this order to the pizza shop, gets the pizza once it's ready, and gives it to Person A. In this story, Person A is the client, Person B is like the API, and the pizza shop is the server. The API helps people get what they want without needing to know how the server (pizza shop) works inside.