A RESTful API is a way of designing an application program interface (API) that uses HTTP requests to access and manipulate data. RESTful APIs allow for the operations of GET, PUT, POST, and DELETE, which pertain to reading, updating, creating, and deleting resources. A WebSocket is a long-lasting connection between a client and a server that allows for real-time bidirectional communication. It operates over HTTP through a single TCP/IP socket connection and facilitates message passing between a client and server.