Subject says it all
I'm probably wrong, but I believe SATA are for internal use (inside a computer) and NAS are for use on an external storage with a bit of redundancy.
NAS are intended for NAS environments, where the drive will be running all the time. They are made of sturdier stuff, both on the physical side and firmware side.
SATA drives are intended for 99% of other use cases. If you're just building a desktop PC or something, you'll want this. Going for a NAS drive is a waste of money unless you know what the difference is already and know you have a need for NAS
The difference is warranty and firmware settings.
Desktop SATA drives go to sleep more often. In some cases they may burn out from constantly going to sleep rather than expected wear.
NAS drives go to sleep less often, if at all.