Literal comes from the Latin word meaning "letter." It means "according to a specific word or definition, not figurative or metaphorical." It can also mean "following the exact words," "made up of letters," or "exact in fact or detail." The adverb form is literally.
A literal translation is a translation that is word-for-word, following the syntax of the original language. A verbal translation is also a word-for-word translation, but it follows the syntax of the second language.
In recent years the word literally has become overused, often having a sense of nothing more than "very" or "really." Avoid its use in this sense.