Answer :

Okay so it was where the President at that time sent out forms to reelect people at the end of his term hoping to get more people with his beliefs in the government before he left, and had the new president that didn't have his same beliefs.
These are some of my Notes on it when I did this,
-Midnight appointees that were appointed after the president left to continue his legacy (John Adams) Anti-Federalist
-Thomas Jefferson didn’t deliver commissions because he didn’t want those judges (Federalist)
Significance: -Reestablished system of checks and balances
-Writ of Mandamus (they have to follow the order from the supreme court to another branch to do it.) was found unconstitutional
- Writ of Mandamus wanted to demand people to do it and get the judges.
-John Adams  
-Power of Judicial Review

       Why it was a landmark case is because it helped prove the constitution, and helped strengthen the government as a whole. Also they can’t boss anyone around, they get to review the laws or whatever instead of giving them more power like before. Hope this Helped. :)