Before v had a analogue signals, then v moved to digital n now in 2014 v started to view High Definition.,then ultra HD
So is mobile network, before it was 2 g , now it is 3 g , maybe it will go to 4 g, n even 5 g
For example on a 2 g network , v get limited data speed, say eg under 1 Mbps to slow signals ,loss of signals,
But on a 3G v get faster data speed , to 4 Mbps.or even more.
Some Asian countries have jumped to 5 g ,they can get a higher data speed ,wider scope of coverage. Etc etc
If anyone wants a more technical difference go to google, they have most if the answers.