DDR4 ram is the successor to DDR3 ram and has many benefits. DDR3 ram is currently what most computers use, and it came out in 2007.
Double Data Rate Fourth Generation Synchronous Dynamic Random-Access Memory
DDR3 ram operates on 1.5 volts where DDR4 ram only uses 1.2 volts. This 20% reduction on power is important in large databases where it can save millions of dollars. Also, a reduction of power consumption improves battery life in smart phones and laptops.
DDR4 ram has the transfer speed of 2133 MT/s – 4266 MT/s.
DDR3 ram has the transfer speed of 800 MT/s – 2133 MT/s.
Due to the increase in DDR4’s speed it can supports more powerful processors.
Currently the cost of DDR4 ram is preventing many people from getting it. As of 3/6/15 16 GB of DDR4 ram costs about $205. That is high considering that DDR3 only costs $130 for 16 GB of ram. Not only does DDR4 cost more, you also need a DDR4 compatible motherboard and processor which are only produced by Intel right now (as of 3/6/15).
i7 5820K Intel processor $390
Intel DDR4 motherboard $244
16 GB DDR4 ram $275
I would not recommend shelling out money for DDR4 until prices fall in 2016. The typical user would not notice any tangible benefits by upgrading to DDR4 ram at this moment. Although the speed bump is nice, you probably will not notice the difference unless you are a high end user.