3G is currently the worlds best connection method when it comes to mobile phones,
and especially mobile Internet. 3G stands for 3rd generation as it  is just that in terms
of the evolutionary path of the mobile phone industry. 4G means 4th generation.
This is a set of standard that is being developed as a future successor of 3G in the
very near future.

The biggest difference between the two is in the existence of compliant technologies.
There are a bunch of technologies that fall under 3G, including WCDMA, EV-DO, and HSPA
among others. Although a lot of mobile phone companies are quick to dub their technologies
as 4G, such as LTE, WiMax, and UMB, none of these are actually compliant to the
specifications set forth by the 4G standard. These technologies are often referred to
as Pre-4G or 3.9G.

4G speeds are meant to exceed that of 3G. Current 3G speeds are topped out at 14Mbps
downlink and 5.8Mbps uplink. To be able to qualify as a 4G technology, speeds of up to
100Mbps must be reached for a moving user and 1Gbps for a stationary user. So far,
these speeds are only reachable with wired LANs.

Summary:

1. 3G stands for 3rd generation while 4G stands for 4th generation

2. 3G technologies are in widespread use while 4G compliant technologies are still in the horizon

3. 4G speeds are much faster compared to 3G

4. 3G is a mix of circuit and packet switching network while 4G is only a packet switching network