Sometimes they'll be leather lined - smooth, soft leather.
I've run cross Miz Mooz ones that have some sort of faux fur lining!!
There are some that have a layer of slippery nylon/polyester with a thin bit of foam behind it (next to the leather).
Then others are just the unlined leather backside of the leather shaft.
The leather lining ones are usually, but not always, better quality.
As long as its comfortable, the lining has never been a problem with my boots. Unlined ones can be harder on tights.