When you buy items online many times you'll have an option of OEM or Retail.
OEM is barebones you ONLY get the item, none of the 'perks'
ie. If you buy an OEM CDROM you'll get JUST the cdrom. No drivers cd (not needed anyways) and no IDE cable that routinely comes with a cdrom.
98% of the time yes they'll work with your machine, assuming its not a 486