You're right that star is 별. But Samsung says it means "three stars" (https://news.samsung.com/global/20-things-you-didnt-know-about-samsung). And apparently, star can also be 성 (https://en.m.wiktionary.org/wiki/%E6%98%9F + https://en.m.wiktionary.org/wiki/%EC%84%B1#Korean). Idk how to explain it further.
성 is simple a different Chinese root or hanja. 별 is a put Korean word. But since quite a lot of Korean comes from Chinese roots some parts can come from a Chinese character, or hanja, that has its own meaning. That being said, you cannot (usually) say a hanja by itself. Hanja are not necessarily words. For example if you want to say 'star' in Korean you would say 별. You cannot say 성. 성 is not a word.
성 is the Korean pronunciation for the Chinese character which means 'star'. A lot of names in Korea use Chinese characters, while the objects have a Korean name. Another example would be the names of the months being x월 (x is the number of the month) 월 is the Chinese character for 'moon. However, when counting months, Koreans use 달, the 'pure' Korean word for moon. 1월 = January, 1달 = 1 month.
Just has to do with the histortical relationship between the countries...you know, invasions and such :) Its a whole topic. But because of historical reasons they used Chinese characters ("Hanja") to represent the language before the transition to hangeul. Same with Japan; even the kana (phonetic syllabary) are historically derived from chinese characters ("kanji". And if youre talking about Chinese languages they have a third name btw - "hanzi")
별 is the native Korean word for 'star'; 성 (星) is the Sino-Korean root for 'star' or 'planet' that's derived from Chinese and can't be used on its own. You must be just beginning your Korean learning, because there are thousands of Sino-Korean characters used in compound words that have native Korean equivalents, and you will not be able to reach fluency until you learn both.
Korean has had several standard systems of romanization over the years, with Revised Romanization currently the official system in use by South Korea and in this course. It came about in the 90s, so proper nouns and words that had previously entered English often make use of one of the older systems.
This gives us Samsung and Hyundai rather than "samseong" and "hyeondae".
-from the Tips and Notes