Tech people like to use "G"s to signify the next generation of technology, especially in the wireless world. There was 2G and 3G, today's 4G LTE and now we are on the brink of 5G.
Yes, but: Marketing people are always getting ahead of the technology people, jumping the gun to get an edge on rivals. It happened with 4G as T-Mobile and AT&T started putting the 4G label on what was essentially a speedier flavor of 3G. The same thing is happening with 5G, as AT&T is slapping the label "5G E" on existing devices that run on its latest 4G network, which it calls "5G Evolution."