API stands for Application Programming Interface. It is a means of communication between two software components. An API abstracts the internal workings and complexity of a software program and allows the user of that API to solely focus on the inputs and outputs required to use it.
When building software, developers rarely write software from scratch and make use of other third-party libraries. An API allows two software components to talk to each other by providing an interface that they can understand.
Another use of an API is to provide data required by an application. Let’s say you are building a weather application that displays the temperature. Instead of building the technology to collect the temperature yourself, you’d access the API provided by the meteorological institute.