A statutory code is a subject-based arrangement of the laws of a general and permanent nature passed by the jurisdiction's legislature. Unlike session law compilations, which are arranged chronologically, codes are well-suited for research because they bring together all of current laws on a given subject in a relatively manageable way.
Many jurisdictions have more than one published "version" of their statutory code. The government adopts one that is "official," i.e. it will govern in the event of discrepancies. The Bluebook prefers citation to the official print version. The official version may be published by the government or a commercial publisher--it varies. See T1 of The Bluebook for the jurisdiction at issue.
Key point: the actual statutory text should be the same, regardless of publisher. The annotations, however, will differ because they're supplied by different editors. Also, officially published government codes, such as the U.S. Code, can be further behind in printing than their commercial counterparts.
Federal: United States Code (official); United States Code Annotated (West); United States Code Service (Lexis)
Massachusetts: General Laws of Massachusetts (official); Massachusetts General Laws Annotated (West); Annotated Laws of Massachusetts (Lexis)
Annotated codes include helpful editorial content such as: references to secondary sources that discuss the statute; references to cases in which courts have interpreted the statute (called Notes of Decision or Case Notes); cross-references to other sections or to relevant regulations; and detailed historical notes.
Unannotated codes simply provide the text of the statute, and thus often are not as useful to researchers as annotated codes. Some unannotated codes (such as the General Laws of Massachusetts) don't even provide references to the enacting session law.