This is the 4854th most frequent Korean word.
관해선
"Regarding" or "about."
관해선 is used here to mean 'in regards to' or 'concerning', pointing to the topic of discussion in the sentence.
이 주제에 관해선 깊이 있는 토론이 필요합니다.
A deep discussion is needed regarding this topic.
Here, 관해선 connects the subject with the ideas associated with his thoughts, showing the perspective or context.
그의 생각에 관해선 여러 가지 의견이 있습니다.
There are various opinions regarding his thoughts.
In this case, 관해선 expresses appreciation in relation to the advice given, underlining its relevance.