The G in 3G and 4G (and earlier versions) stands for "Generation", which is really the generation of tech installed on your phone and at the wireless towers. As new generations of tech emerge they are installed into the wireless towers but do not provide a way to upgrade your devices which requires you to buy a new one to work with the new-gen tech.
"Third-generation mobile networks, or 3G, came to the U.S. in 2003. With minimum consistent Internet speeds of 144Kbps, they were supposed to bring "mobile broadband." There are now so many varieties of 3G, though, that a "3G" connection can get you Internet speeds anywhere from 400Kbps to more than ten times that." (Segan, 2012)
With the release of 4G phones, the perception would be that the 4G would be even faster than the 3G but that hasn't proven to be true in all situations. "There are so many technologies called "4G," and so many ways to implement them, that the term is almost meaningless. The International Telecommunications Union, a standards body, tried to issue requirements to call a network 4G but they were ignored by carriers, and eventually the ITU backed down. 4G technologies include HSPA+ 21/42, WiMAX, and LTE (although some consider LTE the only true 4G of that bunch, and some people say none of them are fast enough to qualify.)" (Segan, 2012)3G service and applications include CDMA 2000, UMTS, EDGE etc.
Phones have become mini-portable computers and now a majority of people use them more for applications (apps) instead of talking. According to Priya Viswanathan of About.com, the pros and cons of 3G and 4G usage are as follows: 3G Networking
* 3G offers much faster data transfers, up to speeds as high as 2Mbps. * Developers can use this network to create maps and positioning services, which are regularly accessed by the younger population. * This network also offers powerful multimedia services for apps such as online billing systems, video conferencing and so on. * 3G is a preferred platform for many popular mobile phone games, especially those which contain graphics and animation. * Advanced developers can also develop apps for mobile TV, IM and video chatting, as 3G supports all these and much more. Cons
* 3G, though available in most parts of the world today, still has to catch on in some nations. Users in these locations may opt for other types of network. The 4G network
* 4G offers is very good for advanced mobile services such as video and movie streaming. This offers much higher speed than 3G or WiFi. * Unlike WiFi, 4G has far expanded coverage and hence, offers more or less constant connectivity. Cons
* Though 4G coverage is expanding rapidly, it still is not available in many locations of world. * Though 4G offers great quality connectivity, it is still in the formative stages and could result in bugs or glitches.
While there's no real consensus of what constitutes 3G and 4G, there are differences in the network architecture between the two. 3G uses a 'Wide Area Cell Based' network while 4G uses an integration of wireless LAN and Wide area. The main difference between the two is that "... 3G networks were designed primarily for voice communications rather than data. On the other hand, 4G is designed especially for data transmission rather than voice. So 4G offers faster access to data using mobile phones. For example, streaming video works better with 4G, with less stuttering and a higher resolution. Similarly, video conferencing and multi-player online games work better with the faster data transmission offered by 4G." ("3G...