“All Web Services are APIs, but not all APIs are Web services”.

Application interface, meaning that one application is able to interact with another application in a standard way – be it over the network or locally.

• APIs can be exposed through local files (such as a JAR file in a Java program, .H file in C/C++ programs, etc.) to allow two local applications to communicate with each other.
• This doesn’t require a network as the two applications are communicating within a single device.

A type of API, which MUST BE accessed through a network connection.

• REST APIs are a standardized architecture for building web APIs using HTTP methods, i.e. they are a type of Web Service since they use HTTP network.