What are the difference between web-applications and iPhone apps?

And what languages are they written in?

Web applications run on web servers; iPhone applications run on an iPhone. Web applications are written in lots of different programming languages where most apps for the iPhone are written in Objective-C.

A web application is a website that looks and acts like an app, but it's not installed on your phone and you can only use it from a web browser (Safari on the iPhone). On the other hand an app is a program that runs alone which you have to install on the phone.

And some apps actually are really just an icon that launches a browser which runs a web app.

As far as which languages, there are a lot of them. Most web apps are written in HTML 5 and Javascript; most iPhone apps are written in Objective C.

In simple words, Web application runs on internet and iphone app runs on iphone device
Web app is written widely in Asp.net (C#.net, Vb.net) and php, perl etc.
while iphone apps in objective-C.

IPhone applications run on an iPhone. Web applications are written in lots of different programming languages where most apps for the iPhone are written in Objective-C.