What is the difference between a MD and D.O. ???????

What is the difference between doctors that are MD's vs D.O.? Some people I've talked to would never go to a D.O. Also can D.O.'s call themselves MD's. There are 2 doctors listed on here as MD's but when I go to their web site they are listed as D.O.'s. Thanks, Robin

We greatly appreciate your interest in helping us build our Q&A database. To discourage vandals from posting garbage, however, we require people to register before posting.