Ake, I'm not going to explain the whole mish-mosh that is U.S. healthcare before and after the Affordable Care Act to you (even if I could) because I don't have time and you apparently have access to the internet, like I do. But, to start you out...

Medicaid (Wikipedia)

Medicaid is the United States health program for certain people and families with low incomes and resources. It is a means-tested program that is jointly funded by the state and federal governments, and is managed by the states. People served by Medicaid are U.S. citizens or legal permanent residents, including low-income adults, their children, and people with certain disabilities. Poverty alone does not necessarily qualify someone for Medicaid. Medicaid is the largest source of funding for medical and health-related services for people with limited income in the United States.

Today's decision on the ACA and Medicaid (NPR/Kaiser Health)

The Supreme Court ruled that Congress has the authority to expand Medicaid, but it can't strip states of all their Medicaid funds if they fail to participate in that expansion. [Currently federal Medicaid funding is an all-or-nothing proposition.] Prior to the court's decision, analysts expected that about half of the people who would gain insurance under the law would do so through Medicaid. Under the Supreme Court's ruling, it's up to each state to decide whether it expands coverage to more people.

If a state does decide to expand Medicaid, people with an income at or below 133 percent of the federal poverty level would be eligible to receive coverage.

Medicaid is one only piece of the pie:

- Medicaid for the poorest (not new, but expanded, with the above qualification), funded by the state and federal governments and administered by each state.

- Private insurance plans for most folks. Most folks are enrolled thru one's employer with part or (rarely) full funding from the employer. Quite often an employee has little choice about the plan they're enrolled in. The self-funded individuals here are those working for small employers who don't offer any insurance benefits, part-time workers who don't get benefits, and the self-employed. There's a lot of variation in the quantity and quality of coverage for this big subset of the population. The ACA is an attempt to sort some of it out.

- Medicare for the elderly and disabled is funded and administered through the federal government. Also not new.

NPR with the Kaiser Health News gives this summary of the effects of the ACA: Health Care Law Upheld: Now What?. Here's the other bit that's upheld with today's decision:

Most people will be required to have health insurance starting in 2014 or pay a fine. That penalty for individuals starts at $95 or up to 1 percent of income and grow in later years. For families it would start at $2,085 or 2.5 percent of household income. The Supreme Court noted in its decision that Americans could choose to ignore the mandate and instead pay the penalty, which they deemed a tax.

and the other part of the answer to your question about poor(er) folks:

People who don't qualify for Medicaid but still can't afford insurance may be eligible for government subsidies. The subsidies would be used to help pay for private insurance sold in the state-based insurance marketplaces, called exchanges, slated to begin operation in 2014.

~ Becky in Tucson