“motion to reconsider is considered made and laid upon the table” & “Madam president… I note the absence of a quorum” What do these mean? Why funny?

In CNN's April 8, 2022 Applause erupts in Senate chamber after Brown Jackson is confirmed there is this little vignette between US Vice President Kamala Harris and the Senate Majority Leader Chuck Shumer that seems to take place after some applause erupts and so I'm guessing is more formal procedure than anything else, but I'm clueless what these words mean:

Harris: Under the previous order, the motion to reconsider is considered made and laid upon the table, and the president will immediately be notified of the Senate's action.

Schumer: Madam president, very happily, I note the absence of a quorum.

[laughter]

Question(s):

1. What do these mean and what is their effect?
2. Does Harris, the president of the Senate's "the president will immediately be notified" refer to Harris themselves, or to the "other president" (i.e. Biden)?
3. What's so funny about "I note the absence of a quorum"?