What is Asterisk (trixbox)?

trixbox® (spelt with a lowercase 't'), is a line of Asterisk®-based IP-PBX products designed to meet the needs of companies from 2 to 500 employees. trixbox comes in two flavors: the open-source community edition and a hybrid hosted solution (which also comes in 3 additional flavours: Enterprise, Call-Centre & Standard Editions).