I need some help about 은, 는 and 이, 가.
My Korean lessons goes very well but theres one thing I can't understand. I almost read lessons like 3 time but still can't get when and where to use 은, 는, 이, 가.

If someone explain it to me clearly it would be amazing!
Thanks a lot.

Question

I need some help about 은, 는 and  이, 가.
My Korean lessons goes very well but theres one thing I can't understand. I almost read lessons like 3 time but still can't get when and where to use 은, 는, 이, 가.

If someone explain it to me clearly it would be amazing!
Thanks a lot.

Answer

The answer above is great. The only thing I'll add is this:

은 and 는 are the same, and the character before determines when to use each one. Ex:

지원은 uses "은" because 원 ends in a consonant ㄴ.
지나는 uses "는" because 나 ends in a vowel ㅏ.

이 and 가 are the same:

지원이 uses "이" because 원 ends in a consonant ㄴ.
지나가 uses "가" because 나 ends in a vowel ㅏ.

The easiest way to remember it is, if the character has symbols on the bottom row, called 받침 in Korean, then you use 이 and 은.

Answer

Quoted from http://www.italki.com/question/250760

1. '이/가' is used for emphasizing a main subject. it could be used as an answer of "누가".

ex)
"누가 청소했니?" 
"철수가 청소했어." 
focused on "철수"

2. '은/는'은 is used for emphasizing an act of a subject.

ex)
"영희는 교실에서 공부해" 
focused on "공부해"

3. '이/가' is used for the first introduction of main character.

ex)
옛날 옛날에 할아버지와 할머니가 살았습니다. 그 노부부는 자식이 없었는데~

4. '은/는' is used for reference of the above-mentioned character.

ex)
옛날 옛날에 할아버지와 할머니가 살았습니다. 그 노부부는 자식이 없었는데~

5. '은/는'is used for comparison

ex)
나는 밥은 좋아하지만 빵은 좋아하지 않는다.
이것은 저것보다 크다.