synching preview and original

Just started using Lightroom cc, so forgive me if this sounds uninformed. I take photos with a Nikon 5600, and generate JPEGs that are about 6 mb in size. When I import (without making any adjustments), what appears in my library are two versions of each photograph, the original 6000x4000 JPEG, and a 500kb JPEG that lists as 1600x1080 (is this just the reduced dimensions?). Is this second file the Smart Preview? My understanding was that editing a Smart Preview would then synch those edits back to the original, in this case the 6000x4000 JPEG. But that doesn't seem to be the case. However, synching works with the same version of the photograph between devices; I edit the smaller file on my iPad and it changes the same file on my desktop, and the same with the larger, original, file. But editing the smaller "preview" file doesn't synch to the larger original. Is this normal, i.e. the synch function works between versions of the same file, but not from a preview to an original? Thank you so much!