There are a lot of abbreviations used in standard numbers. A useful list of common ones and what they mean can be found on the BSI website. The beginning of standard numbers usually indicate the Standard Organisation who published it
Standards can be updated, so it's important to ensure you are using the latest version. Check the status of the standards you find, to make sure you are using the "Current" one.
DRAFT - Standards which are still in the process of being agreed maybe made available in draft form to allow the user community to comment on it. These are not yet "published" standards, so you do not need to work to them, however it's useful to see what is being proposed so you can comment on them.
CURRENT OR EXTANT - Once agreed, draft standards are officially published as current (or in military circles "extant") standards and it is the current version that should be used and/or worked to.
SUPERSEDED - If a standard is superseded it means there is either a later version of the standard – or it has been replaced by another one. You should not be using superseded standards for new works.
WITHDRAWN - If a standard is withdrawn it is no longer valid and should not be used. They may be no new standard to replace these ones. Again, you should not be using withdrawn standards for new works.
OBSOLETE - The standard is no longer needed as technology or knowledge and understanding mean it is no longer relevant. You should not be using Obsolete standards.