First open enrollment period: Oct. 1, 2013, to March 31, 2014

Subsidies: Available for people with income between 100 percent and 400 percent of the poverty level. The 2013 poverty level for an individual is $11,490 and $19,530 for a family of three.

Levels of coverage: The bronze level plans have the lowest premiums but will cover only 60 percent of out-of-pocket costs and typically have higher deductibles than other plans. The silver plans cover 70 percent of costs, and gold covers 80 percent. Platinum covers 90 percent of costs, so it has the highest premiums.

Cap on annual out-of-pocket costs: Cost-sharing such as deductibles can’t be more than $6,350 for individuals or $12,700 for a household of two or more in 2014.

Extra help for lower incomes: People with income between the federal poverty level and 250 percent of the poverty level, which is $28,725 for an individual, can get additional subsidies to help with copays, deductibles and other cost-sharing if they buy silver-tier plans.

Rules for insurers: Insurance plans can’t charge people more for pre-existing conditions, set annual limits or charge older people more than three times what they charge younger adults in the marketplaces.

Number of insurance companies that people have to choose from: From one to 13, depending on the geographic area.

Penalties for not buying insurance: One percent of income, or $95, whichever is more, in 2014.

Exemptions from penalties: You don’t have to pay the fine in several cases for eligibility or financial reasons, including if your income is below the threshold for filing taxes, if you have a financial hardship, if you would have been eligible for Medicaid but live in a state that did not broaden access to it, or if the cost of premiums is more than 8 percent of your income. You’re also exempt if you are an illegal immigrant, in prison, a member of an Indian tribe or part of a religious group that objects to insurance or is in a cost-sharing ministry.

Percentage of Americans who will face the penalty: About 2 percent, according to federal officials.