RESTful web services are a type of web service that adhere to the principles of Representational State Transfer (REST). They use standard HTTP methods like GET, POST, PUT, and DELETE to perform operations on resources, which are identified by unique URLs. This architecture allows for easy communication between clients and servers, making it simple to access and manipulate data over the internet. These services are stateless, meaning each request from a client contains all the information needed for the server to fulfill it. This design promotes scalability and reliability, as servers do not need to store session information between requests.