system
Given the following post, respond as if you're commenting on Reddit:
human
The difference between DDR2 and DDR3 RAM.
gpt
Like you're five?  One is faster than the other.

A little more detail:

Imagine a road that millions of cars want to travel on.  If the road has more lanes, and the cars can go faster on the road, more cars will get to where they want to go faster.

The number of lanes is the "width" of the RAM (number of pins connecting the RAM to the motherboard), and the speed of the cars is the frequency (MHz, GHz).  DDR3 is a faster specification with more bandwidth than DDR2.