With the American taxpayer on the edge of his/her seat right now, the Senate tax bill is headed into the final stretch of this week’s marathon debate over the GOP’s tax-reform legislation and a final vote is expected as early as Friday.Which leaves today wide open for a ton of last-minute fireworks.

A so-called ”vote-a-rama” is expected later Thursday in which various factions in the Republican Party will be horse-trading their brains out as the lawmakers vote on final amendments to the bill.

Here’s your primer:

What is a vote-a-rama?

According to the Senate’s definition, a vote-a-rama is the lawmaking process during which 15 or more votes take place on a piece of legislation in a single day. They can take place for any type of legislation but are often done during budget-resolution hearings. Once the allotted time for debate on a bill expires, any senator may put forward any number of amendments to that piece of legislation. They then vote on the amendments, marathon-style.

How long can it last?

A vote-a-rama can go on for hours.

How did we get to this point?

After the Senate voted 52-48 on Wednesday to start debate on the tax plan, clearing its first important hurdle, the legislative package now goes forward into Debate Land. Vox points out that the centerpiece of the plan “is a huge corporate tax cut, at a time when most Americans think businesses should be taxed more, not less.The top tax rate for the richest Americans would also be cut, and the estate tax for wealthy inheritances would be rolled back.” And now, says Vox, more last-minute changes could be made on the Senate floor during the vote-a-rama, potentially presenting some tough votes for lawmakers on both sides of the aisle and possibly altering the substance of the final plan passed by the chamber.

What’s next?

The Senate would debate the House legislation on the floor for 20 hours, according to Vox, “with that time divided evenly between Republicans and Democrats. That’s 20 hours of debate time, not real time, so the debate could last a couple of days.’ At the end of that debate comes the vote-a-rama.

“At some point, either before or after the vote-a-rama, (Senate Majority Leader Mitch) McConnell would offer the Senate bill as a substitute for the House bill. The timing would depend on whether McConnell wants the amendments brought up during the vote-a-rama to be added to the final bill. This will be a key decision: If McConnell waits until the end to introduce his substitute, then none of the amendments that were added during vote-a-rama will actually be part of the final legislation.”

Can a lawmaker propose any amendment that comes into his or her head?

According to the wonkier-than-thou PoliticalDictionary website, “all amendments must be germane and are voted on consecutively without real debate.During a vote-a-rama, each amendment is considered and voted on for about 10 minutes until they are finished with all amendments.”

Do lawmakers enjoy the process?

It’s an exhausting thing to go through and many senators have said the breakneck pace of a vote-a-rama can make it tough to know what is actually being considered.

What’s a vote-a-rama look like?

Here’s how Keith Hennessey, a former Senate aide and George W. Bush administration official, describes it: Each side gets 30 seconds to talk about the amendment, and they then vote. “The vote-a-rama is an unusual cultural institution within the Senate. All 100 Senators are on the floor, in the cloakrooms, or right outside the Senate Chamber for hours and hours upon end. Another 100-ish staff are packed onto tiny staff benches in the rear of the Chamber, one for Republican staff and another for Democratic staff. Everyone is usually exhausted during the vote-a-rama, which comes near the end of an arduous and usually conflict-ridden legislative battle.”

What kind of amendments might we pitched see this evening?

Republican Senator Susan Collins of Maine, for example, has said it “would be very difficult” to support the tax legislation unless Congress preserves deductions for state and local property taxes and also passes separate legislation to support the individual health care market. Collins is concerned about the Senate bill’s provision to repeal the Obamacare law’s mandate, which requires individuals to buy health insurance or be fined. The bill’s sponsors say repealing the provision could save the federal government more than $300 billion over 10 years.

“I am not committed to voting for this bill,” she said during a Thursday breakfast session organized by the Christian Science Monitor.