A softphone (from software telephone) is a program that enables voice over Internet Protocol (VoIP) telephone calls from laptop and desktop computers and other computing devices, such as PDAs, Vonage and Skype, generally include a softphone application along with the service.
Most softphone applications work in conjunction with a specialized VoIP phone (sometimes called a hardphone) or by using a device called an analog telephone adaptor (ATA) to enable calling from a standard telephone. Sometimes the software can be configured to work with a computer's external or built-in microphone and speakers. The softphone may offer an onscreen display that substitutes for an actual phone, for example when the user is connecting to a laptop, listening through and talking into a headset.
Although IP telephony has been available for a number of years, it's only become widespread very recently. Sound quality, which was an issue, has improved markedly. Furthermore, most providers now enable computer-to-telephone calls, rather than just calls between enabled computers. Given these reasons and the compelling cost savings involved, the growing trend towards IP telephony in homes, businesses, and government offices is likely to continue.