L1 is faster because the CPU checks it first, if the data needed is not in their it moves on down the line to the other pools of cache.

L1, L2 and L3 cache as all the similar in what they are meant for (frequently used lines of data), the only differance is speed and the amount of memory in each level of cache. So if a line of data is not in L1, L2 gets checked as so on until RAM is checked. So there really is no ''differance" in a sense, considering they all exsist on the chip for a reason. One is not nessicarily more important then the other. This is just simply how multi-level caches work.