I have health insurance with my employer and it only covers 80% of the expenses. If I go to the doctor will they bill me for the 20% I have to pay out of pocket, or will I have to pay right then.

i think your employer pays 80% meaning the 20% left is deducted out of your paycheck on a monthly basis . all you have to pay is a co-payment at your doctors for visit it's around 30 to 50 dollers per visit surgery might be $100
the er is another $100 per visit not bad eh with insurance medicine can be free or any where from 10 to 30 dollars not bad either any way thats how it use to work for me when i worked at this factory im pretty sure thats how it works for you to ask your employer. to make sure by the way the prices are from kaiser permanente

The 20% does NOT automatically get deducted from the paycheck!!!!

You will probably have a co-pay that is due at the time of service. You will then be billed for the 20% not covered by your health insurance.

depends on the type of policy u have.
If its cashless, u neednot hvae to pay anything there and then.
If not, u will have to pay the entire amount there and then and later Insurance company will reimburse u the claim amount which may be any percentage of the expense depending on the type of policy, amount covered by the policy i.e sum assured etc.

Always go for a cash less policy.