Triple Sec, Cointreau, Grand Marnier, Orange Curacao-how are they different? I am really confused as they are?

all orange flavored liquers and I wonder what makes them different/similar and can they be used successfully, interchangably in recipes and drinks or is a difference denoted? Any and all information about how they differ or are similar is appreciated.
Update: Great response HeldmyW, but I can't reach you and wanted to ask which would be best poured over vanilla ice cream for a gourmet desert? Can one get away with using triple sec or would there be a distinct flavor difference in using either cointreau or grand marnier?
If anyone knows, please respond.
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