IS RS-232 an input or a output?

RS-232 is a Recommeded Standard (RS) for serial communications. It can be both input and output, or just one or the other. There are RS-232 devices called DCE (for Data Communications Equipment) like a printer, modem, mouse, joystick, monitor. There are RS-232 devices called DTE (for Data Terminal Equipment) like a notebook computer or tower. Two computers may talk to each other over an RS-232 link. The "boss" computer would be the DTE; the "slave" computer would be the DCE. {In practice, nobody really uses RS-232 for intra-computer linking in home or office, but it might be used for fairly long connections on, say, an antenna farm if fiber optics is unaffordable.}