IP address
An Internet Protocol address (IP address) is a numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication.
An IP address serves two principal functions: host or network interface identification and location addressing.
Idle scan
TCP provides reliable, ordered delivery of a stream of bytes from a program on one computer to another program on another computer. TCP is the protocol that major Internet applications rely on, such as the World Wide Web, e-mail, and file transfer. Each of these applications (web server, email server, FTP server) is called a network service. In this system, network services are identified using two components: a host address and a port number. There are 65536 distinct and usable port numbers per host. Most services use a limited range of numbers by default, and the default port number for a service is almost always used.