What are the differences between 1G, 2G, 3G, 4G and 5G?

There's been an evolution in this telecommunications technology over the years, with nomenclatures like 2.5G etc. Recently, Samsung has claimed a breakthrough with 5G: Samsung claims 5G tech breakthrough

What does all this actually mean? How has the technology evolved that would result in it being called "xG"?

Answer :- 

A G is a generation. Within each of those generations there are various competingh standards, and various "half step" improvements.

There is also a lot of marketing spin.

• 1G = analog
  Examples include NMT, AMPS, TACS, etc
• 2G = digital, voice
  Examples include GSM, D-AMPS, PDC
  Some people claim IS-95 original cdma was 3G: I'd say that as a sophisticated 2G

2.5G added data (GPRS)

2.75G faster data (EDGE)

• 3G = digital, supported data, but still circuit switched
  WCDMA, EvDO

3.5G faster data, added packet data onto CS architecture (HSPA)

• 4G = wireless broadband
  OFDMA, flat architecture, true packet switched
  Most people say this is LTE & WiMAX, though some people are waiting for an upgrade to LTE-A (based on a rather silly data rate definition).

4.5G term not widely used but some people say that is LTE-A

• 5G = not yet defined

Much faster. Likely to be real ~2020