[Studio25]

Electronic devices always need their own "operating system" in order to function, even if they aren't capable of having additional features (apps) installed.

In the past, where you bought a phone to make calls and send texts, you had no real idea what operating system was running on your phone, because you didn't need to. That's exactly the same as (for example) a digital video recorder. Who cares what software it's running, as long as it works?

A phone is simply a small computer, so its operating system, processor speed, graphics ability, memory capacity are all factors you might look at when choosing a model - no different than the technical considerations when buying a computer. The operating system (typically ios on the apple products, windows mobile or android on the rest) will determine what type of programs can be run on the device and may be the deciding factor in which phone you choose, or if you're more concerned with style - it's the operating system that determines which apps are available to you.

Tablets such as the iPad are prime candidates for using operating systems originally destined for mobile phones because those systems are slimmed down, and optimised for low power consumption. That also means that if you're able bung a SIM into the tablet, it acquires the features of a phone. It's pointless having calls and texts - you'd just use a phone for that - but the mobile broadband capability is a useful addition to a tablet. "Android 3G" means that the version of Android shipped with the tablet is capable of communicating over the 3G mobile broadband network if the network and SIM are available.