To know about esterification, let us first discuss what an ester is.
An ester is an organic compound formed by the reaction between an organic acid (carboxylic acid) and an organic alcohol. It has a R-COO-Y form where R and Y can be any combining groups - same or different)
The process of formation of ester is known as esterification, that is, this reaction between a carboxylic acid and an organic acid leading to the formation of ester is known as esterification.
Esterification is also used as a test to determine the presence either alcohol or carboxylic acid in a given mixture.