Voice Over LTE (Long Term Evolution)
A standard allowing voice calls to be placed over an LTE network.
Most LTE networks worldwide have been launched initially supporting only data service. A stop-gap technology knows as CSFB allows phones to use LTE for data and other 2G or 3G networks for voice.
VoLTE will allow LTE (4G) networks to completely replace 2G and 3G networks. It will also eliminate the need for CSFB.