Asterisk is an open-source telephony software that started in 1999, transforming computers into communication servers and supporting over 500,000 downloads. It enables the creation of various telephony applications, such as PBXs, VoIP gateways, and call centers, making it a flexible and cost-effective solution for businesses of all sizes. Companies worldwide rely on Asterisk for its extensive features, including unified voicemail, conference bridging, and integrate with existing technology, all supported by a strong community and Digium's maintenance.