Another acronym: API. What does it stand for, what can you do with it and how does it help? What does an application programming interface (API) do? This interface for a program provides other programs with a connection to the interface-leading system. And between programs on an operating system as well as across operating system boundaries and types. APIs are used by software developers, programmers, etc., sometimes they write them too.
An API illustrated
When you drag a graphic from a file manager (Finder, File Explorer, etc.) via drag-and-drop and drop it in a Word document, for example, it seems like a matter of course. However, it is actually only possible because an API exists for this. Staying with the example, you have two applications, the file manager and a word processing program. And in this case, both programs access an API. An API belonging to the operating system in this instance. An interface makes the program boundaries permeable at this point. More specifically, a program interface describes with fixed rules how something can be addressed and processed.
Generally, an Application Programming Interface is distinguished by its – hopefully good – documentation and stability over time. Interested readers can get an overview here: Clipboard Windows and Pasteboard MacOs. It is not hard to see that even as simple seeming an operation as copy-and-paste is quite extensively documented and fills many pages. Other just as seemingly obvious program interfaces represent, for example, the DOM of an HTML document or the way in which map services can be addressed.