Translation is simply the changing of words, most notably a text, from one language to another.
Texts, or words, are translated because the piece is not written in a universal language and for others to benefit from the text, it needs to be changed into another language.
While this seems easy enough, many languages contain words that are not easily translated out of their original. Translators must insure that they keep the word or text as close to the original so as not to alter the intended meaning.
Many times, the original text must be altered to a point where the feeling, message, or emotive qualities have changed. Unfortunately, this is something simply accepted by the literary community. The phrase "lost in translation" comes from this.
Characteristically, translators must be familiar with the language, dialect, literary devices, and ideology of the original author and their texts. Without this knowledge, the translation can become something very different from what the author intended.