There exists an excellent site on which you can find out the key for most of the $LaTeX$ comments.
The site is Detexify Latex handwriting.
The page says:
"Anyone who works with LaTeX knows how time-consuming it can be to find a symbol in symbols-a4.pdf that you just can't memorize. Detexify is an attempt to simplify this search."
What you have to do is just draw the symbol (on the portion given in the site) for which you want to know the comment.
You will be given the latex-code for that symbol.
