What is Asterisk and why do Indian businesses choose it over commercial PBX platforms?

Asterisk is an open-source PBX framework that runs on Linux and supports voice calls, IVR, call queues, voicemail, call recording, and SIP trunk connectivity. Since it has no per-seat or per-channel licence fees, it offers significantly lower ownership costs than commercial PBX platforms, especially for businesses with many extensions or concurrent calls. However, it requires skilled Linux and telephony expertise to deploy and maintain.