Good day to everyone,

I'm hoping some of the more experienced members of this forum will either point me into an existing thread or help fill this one out for all the beginners.
looking through most of the posts on here I have picked up a lot of the abbreviations used but some of the terms used still elude me.
I'll add abbreviations and terms onto this post as and when I come across any that I don't understand. So to start with:

What does it mean when you mention a smile on a razor?