What is the difference between the E12 and E24 resistor series?

E12 ( 10%): 10 12 15 18 22 27 33 39 47 56 68 82

E24 ( 5%): 10 11 12 13 15 16 18 20 22 24 27 30

33 36 39 43 47 51 56 62 68 75 82 91

The basic difference is that the E24 have "extra" values between those of the E12. It's roughly midway between the E12 points. They're more expensive too.

There's also an E6- it runs:

10 15 22 33 47 68

At the top end there's an E192- wildly expensive but extremely accurate. They're used in life-critical systems or super accurate industrial machines.