But it doesn't seem like anybody is actually talking
+ Senate rules (no laws - just internal senate rules) - require 60 votes in order to "end debate" and proceed to a vote on something.
+ Since you can't vote for something without deciding to vote on it - this, effectively means that you need 60 votes to pass anything, since the opposition could instead just continue debating on the subject forever.
+ In the past, you had to actually continue debating -- that is, if everybody stopped speaking, things went to a vote without this rule - so somebody had to physically stand there and keep speaking.
+ This was annoying to everybody, so the senate voted to amend their rules to require a formal vote (needing 60 votes) to proceed to the vote -- which means you don't actually have to stand there anymore.
+ It is 60 votes - again this is an internal senate rule. There are things that require 2/3 majority -- e.g. overriding a presidential veto or convicting on impeachment. These 2/3 majorities are actually written into the constitution or are law.
+ This causes havoc - because it can be impossible to pass bills that really need to be passed. So there are exceptions now written in for budget bills (and more recently for the confirmation of justices).
+ What is a budget bill? This has been interpreted very broadly to include things that have budgetary implications. Thus we see these huge yearly omnibus bills passed by whichever party is in charge --- cram as much stuff into the budget bill as possible purely because it doesn't require a 60-vote majority in the senate.
+ That being said, there is a senate parlimentarian who occasionally says "this has nothing to do with the budget" -- and throws out parts of the omnibus. This happened recently with the democrats plan to immigration reform into the budget bill:
https://www.cnbc.com/2021/09/20/senate-p...udget-bill.html -- democrats had argued unsuccessfully that this would have huge economic consequences.
+ The entire requirement for a 60 vote majority could be killed by the senate (and because its a senate rule, it only needs 50+VP votes to be killed). This was done by the Democrats within the context of court justices (except supreme court justices) - and then done by the republicans for supreme court justices. OTOH, Manchin and others won't vote for this, so Democrats don't currently have the votes to do it.
+ There have also been discussions to bring back "the pain" of filibustering -- e.g. requiring the opposition to actually stand up and filibuster.