The term RESTful is used to describe web services or systems that use the architectural style REST. RESTful is an extension of the concept of REST and primarily indicates that a web service or system adheres to the principles and practices defined in the REST style. It is important to note that the term "RESTful" is often used to describe web services that do not fully comply with all the architectural principles of REST but utilize common concepts. For example, there may be some differences, but the system as a whole remains resource-oriented and uses HTTP for interaction between the client and the server.