Difference between 3G, H, H+, E, 4G

Not everyone knows what the symbols "E, H, H+, 3G,  G" exact means.
These appears along with the phone network in statusbar.
Many would have thought why they keep changing.

These are network band by which your device is connected and thence effects your connectivity speed.



The speeds mentioned in the table above is theoretical and in bit not Byte.
* 8bit = 1 Byte