5G is the name of a new wireless network that overtakes the current 4G network that most phones operate on.
It is designed to lower congestion by a large factor, thus allowing all subscribers in a metropolis to stream in hi-resolution at the same time.
It is being rolled out incrementally, and is expected to hit retail clients in late 2019 (see: When will 5G be available?)
At the launch time consumers can expect access to about 5% of the total network capacity of 20 Gb/s.
This will be a boost of about 20% over the current fastest 4G networks, and will ensure early-days network stability (see: How fast is 5G?)
The 5G standard has been in development since early 2015.