He hoped the people of America would always be satisfied with having a majority to govern. He never wished to see two-thirds or three-fourths required, because it might put it in the power of a small minority to govern the whole Union.
This is the filibuster, described as empowering miniority rule.
Hartley
Col Thomas Hartley, Federalist, PA
A good overview of what the elimination of the filibuster might mean to the Biden administration and the Democrat party.
In 2013, a Democratic Senate majority effectively ended the filibuster for district and circuit court nominations as well as executive branch nominations, and then in 2017, a GOP-controlled Senate ended the filibuster for Supreme Court nominations.
With a Senate majority, Biden can basically choose whomever he wants for both Cabinet and sub-Cabinet roles in federal agencies, as those choices are not subject to the filibuster.