What is "transhab"

TransHab was a concept pursued by NASA in the 1990s to develop the technology for expandable habitats inflated by air in space. Specifically, TransHab was intended as a replacement for the already existing rigid International Space Station crew Habitation Module. When deflated, inflatable modules provide an 'easier to launch' compact form. When fully inflated, TransHab would expand to 8.2 meters in diameter (compare to the 4.4 meter diameter of the Columbus ISS Module).