RS-232C is short for Recommended Standard-232C, a standard interface approved by the Electronic Industries Alliance (EIA) for connecting serial devices. In 1987 and 1991 two new versions were released called EIA-232-D and EIA/TIA-232-E. However, the standard is still commonly referred to as RS-232C, or just RS-232.
RS-232 is the most common standard for serial communication. Recently the EIA has approved successors called RS-422 and RS-423 which will be backwards compatible so that RS-232 devices can connect to an RS-422 port.
On Samsung models, RS-232C is known as Ex-Link.