Esterification and dehydration synthesis I know there are many more terms out there like polymerization, condensation, etc. But the important thing is whether they can be differentiated or not.

In Esterification, which I just learned, needs to have a dehydrating agent when involving bad leaving group, such as $\ce{-OH}$.They are typically Brønsted-Lowry acids. Correct me if I'm wrong.

How does heterolysis work in the case of $\ce{CH3COOC2H5}$. [the reverse of the esterification of ethanoic acid and ethanol]
The reverse of esterification is called "hydrolysis."  The hydrolysis reaction can be performed under acidic or basic conditions.  This link shows the mechanisms involved for both the acidic and basic hydrolysis of an ester.  Each step in the reaction is explained in detail and accompanied by a picture.