"The children are eating jam."
Translation:Les enfants mangent de la confiture.
Look at the noun. All nouns in French has gender masculine or feminine. Gender of some nouns either make sense (homme, femme) but others don't. (personne, victime are always feminine)
It is almost IMPOSSIBLE to identify noun gender. (need lots of reading and with the help of dictionary) however the rule of thumb:
the spelling of masculine nouns usually ends in -age and -eau the spelling of feminine nouns usually ends in -ée, -ion and -té
But rules are meant to be broken...
feminine: cage, image, nage, page, plage, rage, eau, peau masculine: lycée, musée, avion, bastion, billion, million, lion, scion, comité, invité
It's the verb conjugation. Have a look at this. http://www.french-linguistics.co.uk/verbs/table/manger.html#.WzNMoSPmjN4