What API

Application Programming Interface is an interface to communicate with different software using different set of instructions which allows applications to access data and interact with external software components, operating systems, or micro services.

Google isn’t in the business of weather data (yet!), so they source this information from a third party. They do so by means of an API, which sends them the latest weather details in a way that’s easy for them to reformat. 

How API Works 

When you search for flights online, you have a menu of options to choose from. You choose a departure city and date, a return city and date, cabin class, and other variables like your meal, your seat, or baggage requests. To book your flight, you need to interact with the airline’s website to access the airline’s database to see if any seats are available on those dates, and what the cost might be based on the date, flight time, route popularity, etc. You need access to that information from the airline’s database, whether you’re interacting with it from the website or an online travel service that aggregates information from multiple airlines. Alternatively, you might be accessing the information from a mobile phone. In any case, you need to get the information, and so the application must interact with the airline’s API, giving it access to the airline’s data. The API is the interface that, like your helpful waiter, runs and delivers the data from the application you’re using to the airline’s systems over the Internet. It also then takes the airline’s response to your request and delivers right back to the travel application you’re using. Moreover, through each step of the process, it facilitates the interaction between the application and the airline’s systems – from seat selection to payment and booking