Chocoholic is a rather unfortunate and ridiculously popular slang term for a person who likes chocolate a lot. It is a portmanteau of the words 'chocolate' and 'alcoholic' (as in, a person suffering from alcoholism), and was coined in 1961, the same period as sugarholic (1965), workaholic (1968), and golfaholic (1971) (surprisingly, shopaholic was the last of these to be coined, appearing in 1984).
Despite the fact that no one is actually addicted to chocolate and that very few people do not like chocolate, making this word completely redundant, it is widely recognized and has entered a number of dictionaries, including the OED. It is sometimes spelled 'chocaholic', although at this point the word is common enough that we can probably declare 'chocoholic' the one true spelling -- as does my spellchecker.
The more PC and etymologically correct chocophile is sometimes used by those who feel that they are true connoisseurs of chocolate, but it has not yet entered into popular usage.