Any computer (node) connected to a network (usually via TCP/IP) which is directly used by resources (e.g., public domain programs, text/data files, mailboxes, etc.). . It is quite common to have one host machine provide several services, such as WWW and USENET. An Internet host can be identified by its dotted quad address or its distinctive domain name. This computer system may also be the source of network services on which you may hold an interactive session if you are a valid user of that system.

As a verb: To provide the infrastructure for a computer service. For example, there are many companies that host Web servers. This means that they provide the hardware, software, and communications lines required by the server, but the content on the server may be controlled by someone else.