The Affordable Care Act mandates that most people are insured either through their place of employment or purchasing a policy on their own. Remember, beginning in October 2013 there will be options in every state for purchasing insurance through a state-wide Marketplace.
There are exemptions from that mandate for several reasons including financial hardship, which is an official definition based on income and family size. The good news is that, depending upon your income level, you may qualify for a tax credit and/or cost-sharing subsidies from the government to reduce how much you may pay for health insurance purchased through the official marketplace. If you choose not to purchase a policy, you will be required to pay an additional tax every year you do not purchase a policy. That tax will increase each year that you go without insurance. The first year that tax will be either $95 in 2015 or 1% of your income, whichever is MORE.
There will still be a catastrophic-coverage-only type of insurance plan available for younger people and those with extreme economic hardship. Uninsured people will not have to pay the fee if the Marketplace calculator determines their income is too low or a few other reasons. A catastrophic plan can cover essential health benefits but only after you have met a very high deductible (several thousand dollars for an individual up to over $10,000 per family) that you have paid out of your pocket.
Also be sure to check any other special insurance programs and plans for which you may be eligible.