Where is Ubuntu storing installed programs?

ubuntu, ubuntu-10.04, ubuntu-11.04

Solution

If you installed the package with the Ubuntu package manager (apt, synaptic, dpkg or similar), you can get information about the installed package with

dpkg -L <package_name>

Problem

I am using Ubuntu and when I click on a program to download Firefox asks me "What should firefox do with this file?" And in the "Open with" I would like to find a program "Package installer". The problem is - I don't know where to look for. Where is the program stored (I installed it using Ubuntu Software Center)

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