속어 (sogeo) means “slang” or “colloquial language.” It refers to informal words or expressions that are commonly used in everyday speech but may not be appropriate in formal settings

꿀잼 (kkuljaem) means “super fun” or “really enjoyable.”

노잼 (nojaem) means “not fun” “boring”

남친 (namchin) is a shortened form of 남자친구 (namjachingu), which means “boyfriend.” 

The term 남사친 (namsachin) refers to a male friend who is strictly platonic—not a boyfriend.

Note the different writing!
남사.. vs. 남자.. 남사친 = platonic male friend, 남자친구 = boyfriend

여친 (yeochin) is a shortened form of 여자친구 (yeochingu), which means “girlfriend.” 

The term 여사친 (yeosachin) refers to a female friend who is strictly platonic—not a girlfriend.

Note the different writing!
여사.. vs. 여자.. 여사친 = platonic female friend, 여자친구 = girlfriend

뭐 함 is a contraction of 뭣늘 해요 = what are you doing?

함 is a slang form of 하다. to do
임 is a slang form of 이다. to be

현타 is a slang form of „현실 타격“ (Hyeon헌타-sil ta-gyeok), or 현자 타임 or 현실 자각 타임.
It can be translated as “reality hit”, “reality check” or “back to reality”.
It describes the moment when someone suddenly wakes up from an illusion or wishful thinking and faces the harsh truth. People often use it when their expectations don’t match reality—like after failing a test or realizing something isn’t as great as they imagined.