An Application Programming Interface (API) is a way to interact with an external software component.
An API is a set of possible interactions with a software component. For instance, most of us don’t know how an internal combustion engine works but we know how to drive a car. The steering wheel, gas pedal, and brake pedal are like the API of a car. You could then think of digital example like Alexa. Ordering more toilet paper on Alexa is a streamlined version of the full process.
Internet companies like Twitter (social media), Trulia (real estate) and Stripe (payments) provide APIs to interact with their software. For instance, you could analyze tweets from the Twitter API.
You can interact with an API by using an “http request.”
A basic way to use an API is to “read” information from a external software component. A price feed from a financial source is a good example of this.
REST API
A REST API (also known as a RESTful API) is an API conforms to the REST architecture. REST stands for representational state transfer. The REST API was created by computer scientist Roy Fielding.
Resources
What is a REST API? by Red Hat