RESTful API Design Principles

Representational State Transfer, usually shortened to REST, is a set of design rules for applications that talk over a network. Roy Fielding described it in his doctoral dissertation as the style behind the design of HTTP itself. An API that follows these rules is called a RESTful API. Its clients work with named things, such as tasks or users, through the standard HTTP methods, and its responses use standard status codes.

Express does not force you to follow REST. You can register any path with any method, and Express will run it