it's general stuff like family practice, general practice, internal medicine, peds, and ob/gyn. basically like the first people you go to see when you have any problems.
then you have secondary care which are like specialists that the primary care docs refer patients to.
then you have tertiary care which are the big hospitals with a bunch of specialists and high tech gadgets to perform more stuff than secondary care peeps can.
last is quarternary care, which is when all else fails and you pray to God for help. (actually there is something called quarternary care, but I don't know what that really means. probably something even more specialized than what tertiary care provides)