Korean romanization is a system for representing the Korean language using the Latin script. Korean also has an alphabetic script of its own called hangul, and is sometimes written using Chinese-style characters called hanja.
Romaja literally means Roman letters in Korean, and refers to the Latin script. "Romaja" is not to be confused with "romanization". The former can be applied to any use of the Latin script in Korean text—whether for Korean or non-Korean words or names—while the latter refers to writing Korean words using the Latin script: either romanizing individual words in a Korean text, or writing an entire Korean text in the Latin script.