A softphone or a software phone is just like a regular phone except for it works via your computer or mobile device. Also, instead of using a hardline, GSM or 4G the connection works via the internet. Perhaps one of the drawbacks of a softphone is that the quality and number of calls are limited by internet bandwidth. That said it offers many more features than a regular phone and is also a lot cheaper than a conventional PBX system. Plus the per-call rate is much lower than even the cheapest mobile or phone service providers.