People will often use the word "literally" after they use an idiom, if they want to point out that part of the idiom is actually true. For instance:
"She wouldn't hurt a fly."
This means that someone is very gentle.
"She wouldn't hurt a fly - literally."
This means that someone is the type of person who is so gentle, she actually goes to the trouble of catching insects in the house and putting them outside, rather than killing them.
Particularly in America, people overuse the word "literally" -- and they use it inappropriately. When someone says to me, "I literally jumped out of my skin," I ALWAYS remind them that they did not do any such thing! I will say, "Wow, you look great for having had such radical surgery afterward," or something like this. It is LITERALLY a pet peeve of mine.