"That camera is expensive."
Translation:그 카메라는 비쌉니다.
이 - 'This': used when it's something close to the speaker
그 - 'That': used when it's something close to the listener
저 - used when it's far from both the speaker and the listener. The closest thing in English to this would be 'That over there'
If you go on the Tips page of this lesson, you can find a more detailed explanation :)