Keywords vs Stereotypes

What’s the difference between << keyword >> and << stereotype >> ? In component diagram both looks the same but aren’t when ex. you want to hide one or another. what’s the reason of such logic?
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For component the keyword is just part of the notation defined in UML specification (please ask OMG about why they design the notation in this way). In VP you can right click on the component and select Presentation Options > Show Component Options to control display the keyword or not.