What card types can't appear in your library?
Conspiracy, phenomenon, plane, scheme and vanguard.

300.1. The card types are artifact, conspiracy, creature, enchantment, instant, land, phenomenon, plane, planeswalker, scheme, sorcery, tribal, and vanguard.


313.1. Conspiracy cards are used only in limited play, particularly in the Conspiracy Draft variant (see rule 905). [...]
313.3. Conspiracy cards remain in the command zone throughout the game. [...]


310.1. Phenomenon is a card type seen only on nontraditional Magic cards. Only the Planechase casual variant uses phenomenon cards. See rule 901, “Planechase.”
310.2. Phenomenon cards remain in the command zone throughout the game [...]


309.1. Plane is a card type seen only on nontraditional Magic cards. Only the Planechase casual variant uses plane cards. See rule 901, “Planechase.”
309.2. Plane cards remain in the command zone throughout the game [...]


312.1. Scheme is a card type seen only on nontraditional Magic cards. Only the Archenemy casual variant uses scheme cards. See rule 904, “Archenemy.”
312.2. Scheme cards remain in the command zone throughout the game [...]


311.1. Vanguard is a card type seen only on nontraditional Magic cards. Only the Vanguard casual variant uses vanguard cards. See rule 902, “Vanguard.”
311.2. Vanguard cards remain in the command zone throughout the game. [...]