what does the arrow looking symbol mean next to the battery top right?

You mean this:

That means location services is turned on & an app is using location services.

It means location services are active.

There is a section in the beginning of the manual that explains all the little symbols:

http://manuals.info.apple.com/en_US/iphone_user_guide.pdf

Best of luck.

Covered in the manual:

iPhone User Guide (For iOS 4.2 and 4.3 Software)

How to find the app which are currently using Location Services (and get rid of the arrow symbol):

Go to System Settings > Privacy > Location Services > Scroll down to find the app which has a purple arrow next to it > Change its settings from Always to Never