Why is REST API called REST?

The primary goal of API is to standardize data exchange between web services. Depending on the type of API, the choice of protocol changes. On the other hand, REST API is an architectural style for building web services that interact via an HTTP protocol .

Edit: It is called REST, because the client initiates transfer of representations of client state . you should mean “the client initiates transfer of representations of server state.”

Put simply, there are no differences between REST and RESTful as far as APIs are concerned. REST is the set of constraints. RESTful refers to an API adhering to those constraints . It can be used in web services, applications, and software.