what are 3G Technical Specifications?

The first thing you require is a device (e.g. a mobile phone) that is 3G compatible.

This is where the name 3G phone comes from - a phone that has 3G functionality; nothing to do with the number of cameras or the memory it has. An example is the iPhone 3G.

3G phones commonly have two cameras since the technology allows the user to have video calls, for which a user-facing camera is required for capturing him/her.
Unlike with Wi-Fi which you can get for free in hotspots, you need to be subscribed to a service provider to get 3G network connectivity. We often call this kind of service a data plan or network plan.
Your device is connected to the 3G network through its SIM card (in the case of a mobile phone) or its 3G data card (which can be of different types: USB, PCMCIA etc.), which are both generally provided/sold by the service provider. Through that, you get connected to the Internet whenever you are within a 3G network. Even if you are not in one, you can still use 2G or 2.5G services provided by the service provider.