Much of the uncertainty surrounding the impact of President Obama's health care overhaul is wrapped up in insurance exchanges, a new concept that will create online health plan marketplaces.

States must either set up their own exchanges -- organizations set up to provide health plans to individuals and small businesses -- or default to exchanges created by the federal government. People can compare insurance plans -- there will be different plans for various income levels -- and enroll through a specially created website for each state. They can also enroll over the phone or in person.

One likely effect of the exchanges

is a switch to more "community rating," or factoring more people into the equation when assessing health risk to determine insurance rates. Consumers will be judged against a more general average, meaning that younger and healthier people

will be paying higher-than-normal rates and the older and less healthy will be paying less than normal.

"Not only will choice be somewhat decreased, but they may be paying a premium that is not as relevant to their particular situation," said health care lawyer Peter Pavarini. "Of course, no coverage is no choice. For the people covered under Obamacare for the first time, it's great."

Just what the full cost will be, however, remains to be seen. While the exchanges need to be ready when open enrollment begins on Oct. 1 -- they go into effect on Jan. 1 -- governments are still scrambling to meet deadlines and build insurance plans.

Much of the work comes in setting up the marketplaces themselves, whether it's building the website that enrolls residents or setting up phone banks and in-person enrollment centers. Once that's done, governments must invest in outreach to ensure enrollees know how to use the marketplace.

Maryland and D.C. are creating their own exchanges -- both have been given conditional approval by the U.S. Department of Health and Human Services, meaning they're on track to be ready by October. Virginia will be defaulting to the federal exchange.

The waiting game can be frustrating for health care providers and potential consumers.

"For the exchanges, they haven't decided what the basic benefits will be," said Larry Sartoris, president of the Virginia Hospital & Healthcare Association. "All you can do often is guess. I'd have to have a crystal ball to do some of that." - Matt Connolly