There’s a lot of talk about the procedure Republicans are using to dismantle Obamacare, but what exactly is reconciliation and how does it work?

Reconciliation is a budget tool used for legislation that changes taxes, spending, or the deficit. The procedure is especially powerful in the Senate, since a reconciliation bill only needs 51 votes to pass.

This year, GOP lawmakers are taking a crack at repealing the health care law through reconciliation, and the Senate took the first major step toward dismantling the law Thursday.

After a lengthy voting session, the upper chamber passed a budget resolution for 2017 that instructs four congressional committees to start writing the repeal bill.

Senate Majority Leader Mitch McConnell praised his Senate colleagues for taking “an important step” toward repealing Obamacare.

“The American people have called on Congress to act and finally bring relief from Obamacare,” McConnell said in a statement after the Senate passed the budget resolution. “I am pleased that the Senate took this critical step towards keeping that commitment tonight, and I look forward to our House colleagues passing it soon.”

The House is expected to vote on the budget resolution Friday.

Once both chambers have passed the fiscal blueprint, the committees that oversee the Affordable Care Act can begin working on the actual bill that will repeal Obamacare.

They have until Jan. 27—just one week after President-elect Donald Trump’s inauguration—to complete the legislation.