When Carboxylic Acid is treated with Alcohols in the presence of acid as a catalyst it produces corresponding Esters. This reaction is called as Esterification.
Also, this reaction is a reversible reaction and the ester formed can also hydrolyze to produce Carboxylic acid and Alcohol. This reverse reaction is called as transesterification.
The formation of Ethyl Acetate from Acetic Acid and Ethanol in the presence of acid is shown below,