What is the hydrophobic effect? what types of atoms are most likely to be found in portions of molecules or entire molecules that will undergo this effect?

Hydrophobic in simple terms is the "fear" of water.

In chemistry, Ionic salts are technically hydrophilic as they will dissolve in water.
most fats and oils or triesters won't why?

salts are made from ions and their structure contain polar bonds Na+ and Cl-
Fats and oils tend to not have these.

Fats and oils contain many carbon covalent bonds which are non-polar which tend to make the molecule non-polar as a whole, therefore, it can't dissolve in water and is said to be hydrophobic.

Hope that heps :)
NB included a diagram to help.

Ithink d hope that