Jio is LTE mobile network. It is owned by reliance. It provides wireless 4G LTE network( no 2G/3G) and is the only pure VOLTE network( voice over LTE) in India.
Network coverge of jio is pretty good around the 22 telecom circles in India. But sometimes it loses signal completely or partially and sometimes it is not at all recognised by the smartphone, you need to restart it to regain the signal.
Now Jio comes as new year offer which will provide free data, calls, video, music, tv shows etc till 31st march, But the data is now reduced from 4GB to only 1GB /day which is quite sufficent.