API
An API is a defined way for one piece of software to ask another for data or actions.
Definition
An API is a defined way for one piece of software to ask another for data or actions. On the web it usually means a URL you send a request to and get structured data back.
Use case
A weather widget asks a weather API for today's forecast. The shape of that data decides what your design can show.
Related terms
Documentation
API
A short, clear definition with examples of web APIs you already use.