The 은 (eun) and 는 (neun) are postpositions. Postpositions are used to define the case of a noun, or the grammatical relation between the words. Postpositions do not exist in the English language so this will be an abstract description.
은 (eun) and 는 (neun):
There are at least two applications for 은 (eun) and 는 (neun): contrast and topic marker. In short, contrast defines the sentence style (Question or answer) and topic marker defines the subject in a sentence. Just like before; if there is a batchim, use 은, if not, use 는.
In practice – contrast:
The question uses 이/가 and the answer 은/는.
수나가 학교를 갑니까? (sunaga haggyoleul gabnikka) – Is Suna going to school?
In practice – topic marker:
Noun’s with a 은 (eun) and 는 (neun) in the end become the topic of the sentence. With every sentence about a persons action, use 은 (eun) and 는 (neun). Otherwise use 이/가 .
저는 읽고 있습니다. (jeoneun ilg-go issseubnida.) - I am reading