Most players on the PS4 get a wireless usb keyboard in order to communicate with the general population, which I highly recommend. A cheap kb will do. There is no voice chat supported by XIV itself. Some PS4 players will join PS4 linkshells or Free Company's and use PS4's party chat system to talk to each other. My FC has both PC and PS4 players, we all use keyboards to talk in general although sometimes I'll chat with the other PS4 players via PS4 party chat as well.

Players mostly socialize via Free Companies (guilds), Linkshells, party or tells. If you have a question you can /sh to the zone and will probably get an answer depending on the time of day, and there can be some general chit chat in popular areas like Revenant's Toll and the Manderville Gold Saucer but people generally use the private channels to talk. The Gold Saucer will be accessible after a lvl 15 quest in Ul'dah, and the Main Scenario will take you to Mor Dhona/Rev Toll in the 40's although you can make a run for it earlier if you take a chocobo and stick to the roads.