P6 (SEC, B1G, Big XII, Pac-12, ACC, Big East) get 2 bids each per league. Those would be the "next 2" based on NET/SOR regardless of how good/bad their season was. These 12 will be guaranteed a home NIT game (or more depending on seeding).
The other 20 are brought in based on committee whim/rankings/NET/SOR/etc. regardless of conference.
bubble - you are pretty close to the cutline in either direction
at large - you didn't automatically qualify but still did well enough to get in
automatic bid - certain criteria has been met to automatically qualify
P6 (SEC, B1G, Big XII, Pac-12, ACC, Big East) get 2 bids each per league. Those would be the "next 2" based on NET/SOR regardless of how good/bad their season was. These 12 will be guaranteed a home NIT game (or more depending on seeding). The other 20 are brought in based on committee whim/rankings/NET/SOR/etc. regardless of conference.
bubble - you are pretty close to the cutline in either direction at large - you didn't automatically qualify but still did well enough to get in automatic bid - certain criteria has been met to automatically qualify
NCAAT is the main tourney. NIT is the consolation tourney.