The sound card must support full duplex operation, so that both sides can talk at the same time without cutting each other off. Most audio chat software also supports video. Good audio reception performance requires both parties to use a headset with an integrated noise cancellation microphone. This will eliminate feedback from the speakers and minimize room background noise. Internet enabled telephone conversation can be implemented in three ways.
None provide video.
You call the local phone server using a local access number. The local phone server connects to the remote phone server via the Internet. The remote phone server makes a local connection to the desired party. This type of service is currently being heavily marketed to businesses. This type of service does not have a video option.