5G is a new radio access technology developed by 3GPP for the fifth generation mobile network. It will deliver new levels of performance and efficiency that will empower new user experiences and connect new industries such as health, autonomous vehicle, gaming, massive IOT and connected home. 5G will deliver multi-Gbps peak rates, ultra-low latency (the delay between the sending and receiving of information), massive capacity, and more uniform user experience.
The other mobile network generations are 1G, 2G, 3G and 4G.
No, 5G service will be provided to you by default once you obtain a 5G capable device.