These are the three endings you gain in Metroid Prime.  Unlike the other games and how have to beat the game in a certain amount of time, Metroid Prime has you scan things.  The more you scan, the closer you come to a better ending.
74% and below- Once you destroy the Metroid Prime, a cinema will begin showing Samus getting on her ship and staring at the explosion.  She begins to take her helmet off and then the credits will roll.

75%-99%- Once you destroy the Metroid Prime, a cinema will begin showing Samus getting on her ship and then she takes her helmet off and stares at the explosion.  The credits will then roll.

100%- Once you destroy the Metroid Prime, a cinema will begin showing Samus getting on her ship and then she takes her helmet off and stares at the explosion.  The credits will roll and at the end, you see a pool of Phazon and a hand comes out of it and an eye is on the hand. 
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