Voice over LTE - what does it mean for you? Basic level explanations in PCWorld's article. What is VoLTE? Why is VoLTE necessary? When will VoLTE start to show up? and so on. \pcworld.com
VoLTE is a service to make and recieve voice calls though LTE network. AT&T, Verizon, Sprint and MetroPCS will support VoLTE soon (until the end of 2013 I assume) and a lot of operators worldwide. VoLTE probably will put to end "minuts of talk" paradigma, so be prepared!