Difference between pc3-10600 and pc3-8500

looking at upgrading my memory for macbook pro.


apple store offers,
Apple Memory Module 8GB 1333MHz DDR3 (PC3-10600) - 2x4GB


ebuyer offers
Type DRAM
Technology DDR3 SDRAM
Form Factor SO DIMM 204-pin
Memory Speed 1066 MHz ( PC3-8500 )
Latency Timings CL7 ( 7-7-7-20 )
Data Integrity Check Non-ECC
RAM Features Unbuffered
Supply Voltage 1.5 V


WHAT IS THE DIFFERENCE???????????