1 is an acoustic performance that has some lyrical changes towards the end, as well as a complete tempo change, with the song being played much slower and which more emphasis on Vedder's voice. There are also no drums in this version, with the percussion being played on a set of bongos.
This refers to a specific version of a song that is performed acoustically with altered lyrics, a slower tempo, and a focus on Eddie Vedder's voice.  It omits drums and utilizes bongos for percussion.