01. The base of infinite or boundless space.
This is akasanancayatana jhana a meditative state where the mind contemplates the infinity of space.
02. The base of infinite or boundless consciousness.
This is vinnanancayatana jhana - a meditative state where the mind is absorbed in realizing that consciousness is infinite.
03. The base of nothingness.
This is akincannayatana jhana a meditative state where the mind contemplates the idea that nothing is there.
04. The base of neither perception nor non perception.
This is vevasannanasannayatana jhana a meditative state of neither perception nor non-perception.