Lowers what you pay each month
A federal tax credit applied to your marketplace premium. You can take it in advance so your monthly bill is smaller, or claim the whole thing when you file your federal tax return.
Savings
Two different programs get called subsidies. One lowers your monthly premium, the other lowers what you pay at the doctor, and only one of them requires a Silver plan.

Two kinds of help
They are calculated differently, they apply differently, and one of them is easy to forfeit by choosing the wrong metal tier.
A federal tax credit applied to your marketplace premium. You can take it in advance so your monthly bill is smaller, or claim the whole thing when you file your federal tax return.
Extra savings built into Silver plans for households whose income qualifies. They raise what the plan pays, so your deductible, copays, and out-of-pocket maximum go down.
If your household income is low enough, you or your children may qualify for Medicaid or CHIP instead. Those programs accept applications all year, with no enrollment window.
If you are offered job-based coverage that meets the federal affordability and minimum value standards, or you are eligible for Medicare or Medicaid, you generally cannot use a premium tax credit.
The mechanics
Keep it accurate

At a glance
Good to know
Your household
Enter your ZIP code to see marketplace plans with your estimated savings already applied.