"The men eat fish."
Translation:Los hombres comen pescados.
comer is the verb "to eat".
I eat = yo como; you eat (informal) = tú comes; he / she / you (formal) eat = él / ella / usted come; we eat = nosotros comemos; they (men) / you (plural) eat = ellos or ellas (hombres) / ustedes comen
this is a regular '-er' verb... don't get caught up in the why's. Just memorize the conjugations. Otherwise you're not going to stand a chance when you get to the irregular verbs.