p and s polarization: (forget about their Greek/German/? equivalent) Here p means "plunge", s means "stick". Because p light is easier to penetrate (plunge into water) whereas s light is easier to be reflected (a stick bounced from water).
At Brewster angle, the reflected beam is purely s-polarized, meaning the p-polarized light has zero reflectance. Wikipedia [1] has an excellent image to show this effect:
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Reflectance vs incident angle is below (for 532nm and fused silica):
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At Brewster angle (~56o), reflectance of s-polarization is about 14%.
References and notes
[1] http://en.wikipedia.org/wiki/Polarizer