There are two ways (usually) that you can log onto the console, if you have a monitor and keyboard attached to the system then that would be your console. If you do not have a monitor and keyboard then the system uses serial port A for console connectivity, you would have to connect a terminal or a pc running terminal emulation to the serial port.
In a datacenter environment where there are a lot of systems, the serial ports of all the systems are connected to a terminal server. The terminal server would have an ip and each serial port would be assigned a port number, and you would telnet into the port -
telnet xxx.xxx.xxx.xxx yyyy where xxx is the ip address of the terminal server and yyyy is the port number of the serial port you are trying to console into.