we dont use that words (which, who ,,) for define something , i dont know how can i explain this but i can give some examples senin gittiğin ev : house which you went sevdiğin birisi : somebody who you love i went to the place where you used to live(eskiden yaşadığın yere gittim) i ate the food that he cooked(onun pişirdigi yemeği yedim) place where you used to live(eskiden yaşadı--ğın-- yer) food that he cooked (onun pişirdi***ği*** yemek)

Yes, those two sentences are exactly right. I suggest you go to one of the many online English language sites and search 'Relative Pronouns'. You'll find explanations about how to use these words and some examples and exercises. If you have any specific queries about a particular use of these words, then come back to us here and we'll be glad to answer your question.