what is the diffenence between i-phone and simple mobile phone?
The difference is quite huge: In a few words, the i-phone is a smartphone which offers many services: internet, multimedia, application management... In another hand, a simple mobile phone is a device used to make calls, that's all!
Another point of difference: we develop applications for iPhone using C# and Java(J2ME) for a simple mobile phone!
>>...what is the diffenence between i-phone and simple mobile phone?
It is a really huge subject and you need to be more specific about the second device. A simple answer - They could have different CPUs and could ran different operating systems.
Well, if this question is related to applications development - than Objective-C (Cocoa Touch) is for iPhone. If not Objective-C - it's anything else.
If this is a general question - than you should check with wikipedia first:) for instance "smart phone" vs "feature phone". It is really too general.