What are the tools (hardware/software) required to develop iOS applications? Because I want to learn iPhone application development.
You'll need a Mac (any current model will do) and Xcode which can be downloaded from the Mac App Store. It comes with all the tools necessary, including a Simulator. It nevertheless is recommended to test apps on the hardware (aka an iPhone) as well.
Additional details can be found here.
If Xcode is too complex, you might consider something such as Xojo. With Xojo you can make native iOS apps (and more) using easy drag and drop and Visual Basic-like coding.