It's just a lower voltage version. In terms of voltage used, DDR uses more than DDR3L that uses more than LPDDR3. Not all Intel chips support all voltages though. DDR3L chips work both with DDR3 and DDR3L voltages though, but to run with the lower voltages of DDR3L, they're usually better chips that don't need as much juice, and therefore also run cooler. If I remember correctly, DDR3 is 1.5V and DDR3L is 1.35V