how to do to run or activate an action with the click of a mouse?

I'm new in Unity3D, I know how to do to run or activate an action with the click of a mouse, because my intention is to move the main camera according to how I move the mouse.

Thank you all for your time.

http://unity3d.com/support/documentation/ScriptReference/Input.html

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http://unity3d.com/support/documentation/ScriptReference/Input.GetButton.html