> I don’t understand the filibuster thing and how it plays into this.
Senators are allowed to debate bills. A motion to end debate and move to vote can't happen until debate ends. A senator does not generally have a time limit on the amount of time they can debate, so unless they yield the floor, the process can't move forward.
Cloture is a process to force a closure of debate to force a vote (which has its own separate rules). This requires 3/5 of the senate to vote in favor of ending debate. In practice, senators are not speaking for hours on end anymore; it is simply the "threat" of filibuster which eventually stops the bill in its tracks. In this state it cannot progress to a vote nor does it go back to the House of Representatives. In order for it to proceed, they must pass it (and send it to the president) or amend it (and it goes back to the house of representatives).
> I’m seeing the vote for the government budget or something being voted on over and over. If there is a certain majority required to pass something then it is implied that there are negotiations. If the opposition party was just expected to vote yes then why vote at all?
There is negotiation. Senators may try to convince each other to vote a certain way so they can gather enough votes to force cloture. This isn't a formal debate on the senate floor, but done behind the scenes. This may result in them finding enough votes to force the vote or it may result in an amended bill. If a bill is amended by the senate, it must go back to the house of representatives to be voted on. If it passes there, it moves on to the president. If it is amended, it goes back to the senate. Once both houses pass without amendments, it moves on to the president.
> If the opposition party was just expected to vote yes then why vote at all?
Currently they need 6 or 7 votes to pass. They have a few Democrats voting with the Republican majority and Rand Paul, a Republican, is voting against the Republican majority. In order to get the supermajority for cloture, they need to convince several more Democrats. It can happen, though without real amendments, it's unlikely.
> That’s why I’m asking, has the content of what was voted on changed significantly? Maybe taking away healthcare from people has to be done a different way. Make a bill that opens the government, then take healthcare away.
The reason why the Democrats are holding as of right now is because of expiring Affordable Care Act subsidies. If the bill opens the government without an extension, then it is taking that healthcare away, as you say. They are using the shutdown and the increased pressure on the government to reopen as leverage to extend these subsidies. The short term pain is dwarfed by the perceived benefit of ensuring that the funding for these subsidies is secured.
For the Republicans it is essentially the opposite. Extending these subsidies leaves it open to being a wedge point again down the road and midterm elections are coming up next year. They are using the shutdown to try to convince voters that Democrats don't care about government employees or other people because they won't fund the government (i.e not paying US service members, Air Traffic Controllers, Federal workers, etc.). Extending Affordable Care Act subsidies goes against their stated interest in aggressively reducing budgetary deficits over the next ten years.