Intel and Micron Technology have been working on a new-generation memory technology since about 2012. It's called 3D XPoint (not to be confused with 3D NAND), and it's absurdly fast. A good way to think of it is as a compromise between the speed of DRAM and the capacity of traditional flash storage. Unlike RAM, 3D XPoint is non-volatile (doesn't lose what it's storing when the power is off), and it's about four times denser. It's more expensive per gigabyte than NAND flash — the current technology inside SSDs — but it's faster in nearly every possible way, especially when it comes to latency and reading / writing small bits of data.
Now Intel has started shipping its first product with the new technology: the 375GB Intel Optane SSD DC P4800X. It's a $1520 PCIe card, working on the same NVMe standard that's popular for traditional SSDs right now.
Intel has offered a few publications a chance to check out the card, but for whatever reason it's being very secretive about its new storage baby. Reviewers like Billy Tallis from AnandTech and Paul Alcorn from Tom's Hardware had to access Intel's own servers remotely to test the card, instead of putting it inside their own computers for testing.
From looking through those tests, 3D XPoint appears great in nearly every way. For the right sort of tasks that are I/O limited but don't require terabytes of storage, 3D XPoint is the new king. While it's mostly just for enterprise right now, might require some changes in software to utilize to the utmost, and won't destroy the NAND or RAM markets anytime soon, it's nice to have a new challenger on the scene.