How will a pos differ from hmos and ppos?

HMOS.PPOS,POS. Hmos all care is given by your primary care doctor, and to see specielist you need a referrall, ther may be a copay pos give you a choice of hmo through your pcp or you can go outside the network with deductibles and copays etc. Ppos are the best of the lot, you can go to any participating pcp or specielist without any referal, you may have to pay copay, but does not cover non participating provider.