Any device on a TCP/IP network that has an IP address. Examples include servers, workstations, network-interface print devices, and routers. The terms “node” and “host” are often used interchangeably in this regard.
Sometimes the term “host” means a device on a TCP/IP network that can both receive data and initiate contact with other devices. For example, a computer configured as a Simple Mail Transfer Protocol (SMTP) host receives e-mail messages and forwards them to their destination.
In mainframe computing environments, a host is a mainframe computer that is accessed by users through remote terminals.