Q. What are the hydrophobic molecules (or hydrophobic molecular regions)? What are the hydrophilic molecules? How can they be characterized in relation to their polarity?
Hydrophobic molecules are those that have no or little propensity to dissolve in water (hydro = water, phobia = fear). Hydrophilic molecules are those that have great tendency to dissolve in water (philia = friendship).
Water is a the polar substance. Keep in mind the rule that "equal dissolves equal" one can conclude that hydrophobic substances are non-polar molecules while hydrophilic molecules are polar molecules.