In a nutshell: you use "qui" (=which/what) as the subject of a subordinate clause to refer to a noun in the main clause. If there is no clear target in the main clause to which "qui" can refer, you use "ce qui" (=that which). 1) Ce qui m'interesse, c'est la musique. -- What interests me is music. 2) La musique, qui m'interesse, est le jazz. -- The music, which interests, me is jazz. In the first example the "what" has no clear target in the main clause, hence "ce qui" is used in French. In the second example, "qui" refers directly to "music" and therefore you can use it by itself. Greetings, -- Chris (not a native speaker).