In terms of biology hydrophilic mean being polar. Where as hydrophobic means non-polar.

Polar molecules can dissolve in water. For example table salt, or sodium chloride is a polar molecule because of its ability to dissolve in water.

Observe the animation bellow. Sodium chloride (NaCl) is added into water (H2O). Sodium chloride is made up of a positively charge sodium ion and a negatively charged chloride ion. Water is made up of 2 slightly positively charged hydrogen ions, and one slightly negatively charged oxygen molecule.

The Positive hydrogen molecules are attracted to the negative Chloride, and the oxygen to the sodium. The water molecules wedge their way into the molecule and break it apart. This is why salt dissolves in water. The animation below shows salt dissolving in water. Notice how salt is a cluster of sodium and chloride molecules.

Non-polar molecules, such as fats contain large amounts of Carbon and hydrogen bonds. This makes them non polar.

The image below is a fatty acid.

To learn more about lipids, and their necessity in life click here.