은/는

The topic marker identifies what the sentence is about - the "topic" of discussion. This is different from the subject marker 이/가, which identifies who or what is performing the action. The topic of the sentence can also be the subject.

We have a lesson explaining the difference between the subject and topic marker. You can read it here.

The topic marker has other uses:

Conjugation

All Tenses
N (V) 딸기 딸기는
N (C) 수박 수박은

Changes

When used with certain words Koreans often combine them together. It isn't required to do so though.

Example Sentences

Polite

저는 이름이 서연이에요.
My name is Soyeon.

Polite

저는 한국 사람이에요.
I am Korean.