Also known as "videophone", or "video conferencing", this feature lets two people with 3G video phones talk to each other while viewing 2-way live video of each other.
Some phones with this feature have a camera that rotates or swivels, so it can face the user for video calling, and face "out" for taking photos. Other phones have two cameras - one facing in and one facing out.
This feature requires a 3G network that specifically supports video calling. It will only work when the phone is in range of such a network. Both phones must also support video calling - not all 3G phones do.
A one-way variant also exists called "video sharing".
See: Video Sharing