The Air Force today still operates in both air and space, though the new department – the Space Force, itself a subsidiary organization of the Air Force like the USAF was for the Army back in World War II – will progressively take
on those challenges and responsibilities over time.
It was adopted in 1804 and changed the exact procedures for how the electoral college can elect both the president and vice president. More specifically, it decrees that each electoral college elector has to cast a distinct vote for the president and vice president.
Previously, electors cast two votes for the president alone, and the runner-up became vice president.
It had ancillary effects for the rest of the voting process, as well.
For instance, it made it so that the House of Representatives votes for the president if the electoral college vote does not produce a clear majority. This is one of the most complex amendments in the Constitution, so be sure to study it in more detail.