The first word in an ester name refers to the alcohol while the second refers to the acid.
e.g. n-Butyl acetate is the ester formed by the reaction of the alcohol (n-butanol) with the acid (acetic acid) to eliminate water. By convention, the structure is usually written with the acid group first, as in CH3COOC4H9
n-C4H9OH + CH3COOH ::equil::CH3COOC4H9 + H2O