Every month Google releases an Android Security Bulletin update which includes patches for security vulnerabilities found in Android. Some OEM partners combine their monthly security updates with the latest Android Security Bulletin to ensure that every month they're sending out an update that ensures their devices remain safe. Samsung does this too and today the company has detailed its February 2017 security patch.
Samsung's February 2017 security patch includes all of the patches in the Android Security Bulletin release for this month, there are a few dozen of them, and it also patches 7 Samsung Vulnerabilities and Exposures (SVE) that are exclusive to the company's devices. Samsung has patched a handful of privately disclosed vulnerabilities with severity ranging from low to medium in this release.
Now that it has detailed the February 2017 security update, you can expect to start seeing it being rolled out over the coming weeks. It's going to take a lot of time before this security update is out for all compatible devices but the process will now begin soon.