HH, ( above) an acoustic guitar is a guitar with its own sound box ( body) which can be played without any further acoustic devices ( amplifiers, loudspeakers etc). The problem is that acoustic guitars can and are played with amplification to boost the sound, and unless you enquire carefully you'll never know what a venue has in mind when it advertises 'acoustic'. I am involved in some 'acoustic open mic'sessions, where instruments that are capable of bring played acoustically are plugged in, and a folk night that is 'totally acoustic', e.g no electrics. people still turn up at both expecting to plug in keyboards etc!