Here's why:

* Esters have the general structure R-COOR', where R and R' are alkyl or aryl groups.

* Ethyl acetate has the formula CH3COOCH2CH3.

* The -COOCH2CH3 portion of the molecule represents the ester group, with:

* -CO- being the carbonyl group.

* -OCH2CH3 being the alkoxy group.