What are liner socks?

Question

are they just to wear in your sleeping bag?

Answer 1

lol, i thought they were the wee half socks you were with trainers!

Answer 2

You can get liner socks for inside walking socks too, as walking socks are coarse and chafe, creating blisters if worn by themselves...but then, as has been said, there are also trainer liners so people think you're not wearing socks and cn admire your ankles...