It has been a while since this question was first asked, but it's still relevant, because this info is still a little tough to track down on the web, so here is a little more info.
I have these same two mystery SMART attributes on my Kingston HyperX Fury, which uses the Sandforce SF-2281 controller.
As already stated, these two numbers track "Host Writes" (234) and "NAND Writes" (233).
These SMART attributes keep track of the wear level on the SSD's Flash memory by recording how much data has been written to the drive.
The reason that two different attributes are needed, is because the SandForce 2000 series controllers try to maximize the life of the Flash Memory by applying "Durawrite" data compression to the data your operating system sends to the hard drive BEFORE it writes it to the actually Flash Memory.
Then when your O.S. reads the data, the controller transparently decompresses the data so that bit-for-bit it is identical to the original.
The reason they do this is that by compressing the data stored on the drive, they can write fewer bytes to the Flash Memory over the life of the drive, which causes less wear and tear and makes the Flash Memory Chips last longer.
... but not ALL data is compressible, so sometimes "Durawrite" compression is really effective, and sometimes not so much, so these two attributes keep track of how much benefit you are getting from the compression.
Here's how they work...
The HOST Writes (attribute 234 on my Fury) duplicates the "LBAs written" attribute (241 decimal on my Fury SSD) and returns the same value, which just keeps track of the TOTAL amount of data, in Gigabytes, that your Operating System has written to the SSD during its full life since first installed.
"NAND Writes" (attribute 233), shows how effective "Durawrite" was at compressing the data by showing the TOTAL number of Gigabytes of data that was ACTUALLY WRITTEN (after compression) to the NAND Flash Memory.
Normally the "NAND Writes" will be smaller than "HOST Writes" with the ratio being controlled by how compressible the data you store on your hard drive is. Things like your browser cache (HTML) compress really well, but already compressed formats like ZIPPED data, JPGs, MP3s, and H264 or MPG video don't compress much at all because they are already highly compressed, so if the drive is used mainly to store that kind of data, HOST Writes and NAND Writes will be almost the same.
Remember BOTH numbers are in Gigabytes, and neither one is associated with a problem of any kind, they just help you keep track of total SSD usage. With 3K cycle Flash chips a 240 Gigabyte HyperX Fury 3K can survive more than 700 terabytes of total writes (700,000 Gigabytes) even for non-compressible data.