The whole PC/PC2/PC3-xxxx is largely marketing nonsense, & is honestly, a stupid naming convention that needs to DIAF, IMHO.
It refers to maximum theoretical bandwidth.
So for PC3-10600, we have a theoretical bandwidth of 10600 MB/s.
The DDR3-xxxx is the frequency the RAM operates at, the number that actually matters.
DDR3-1333 runs @ 666 MHz, double data rate (DDR3-1333).
Do not pay any attention to the PC3-xxxxx rating, like i said, it's a largely meaningless number, & as you can see, some manufacturers arbitrarily choose higher/lower ones than the normal calculation allows for.
Normally, you calculate 8x to get the PC-xxxx rating.
So for DDR3-1333.33 x 8 = PC3-10666.66
Here are some articles that do a better job explaining it that i can.
http://en.wikipedia.org/wiki/DDR_SDRAM
http://www.hardwaresecrets.com/article/167/1