There are two types of remote extensions as you see in the pictures. The ones in blue and the ones in green that are tagged with nightly
at the end. They are both developed by microsoft and I can't see any difference between the two Remote - SSH
extensions.
What is their difference?
Remote - SSH
is the stable version and the Remote - SSH (Nightly)
is the "nightly" build, meaning it contains the newest features that are not considered stable yet.
Actually, the build/release doesn't seem to be strictly nightly, but nightly is generally used to mean the latest and greatest.