What is central limit theorem

CFA Level I
#1

Can ne1 pls elaborate on what " central limit theorem " says, with an example? SS3 reading no 10. Thanks

#2

http://lmgtfy.com/?q=Central+Limit+Theorem&l=1

#3

http://www.elanguides.com/samples.php Their quant videos are all up there. Great explanations of z-scores and hypothesis tests as well!