It's Apples choice in programming language for it's iOS and OS X platforms. It is built upon C, with object oriented features added. Objective-C is influenced by Smalltalk in the way it handles classes and methods.
It depends entirely on what sort of programming you want to do:
1) For web I'd say javascript
2) For iOS I'd say objective c (not a lot of choice there!)
3) For Android it's Java + XML (not a programming language!)
4) For native windows exe's it's C, C++, C# (C# is probably the easiest of those)
5) For pretty much anything (except iOS and android) you can use python, that runs on all desktop platforms and is powerful. It can be as easy or hard as you want it to be and is an excellent language to learn from. See The Python Tutorial — Python v2.7.3 documentation for a good start
It *is* a framework rather than a programming language. It provides libraries and several languages that can be used with them - VB.NET, C#, F#, Eiffel, P#...