basically same thing just ddr5 ram has higher frequencies then ddr3 has, which is why its used on graphics cards , ddr3 atm highest system ram u can get for mb ram slots use
no doubt some1 else give better answer not really up on technical stuff like that
GDDR5 is based on DDR3 but has double the bandwidth of DDR3 (hence why you often see a base clock and then an "effective clock" beside it in parentheses which is simply that base clock multiplied by 4 [instead of 2 with normal DDR3 memory]). Graphics cards require memory that's extremely fast to operate optimally so instead of slapping on the "slow" DDR3 memory, they optimised it to have twice the bandwidth giving it a much higher effective speed. It is more expensive than the traditional DDR3 and requires more power and creates more heat.
Yep, and you can overclock it if you can be bothered (quite difficult for little performance boost, so most dont bother.)
Graphics card memory can be overclocked quite easily though and leads to a decent boost in performance.