"en" and "y" are pronouns that replace indirect objects, i.e. objects that are introduced by "de" and "à" respectively. The use of "de" or "à" depends on the verb and must be learned together with the verb. E.g.: Il se souvient de son enfance. --> Il s'EN souvient. Il va à Paris. --> Il y va. Since partitives are introduced in French by article "de" (in English, the noun is used without any articles), "en" is also used to replace direct partitives: Il a du pain (He's got bread) --> Il en a. Remark: in the case of "à", if it introduces a person, the corresponding indirect personal pronoun (me, te, lui, nous, vous or leur).

Hi Emma. "y" is also used for places, wether it's introduced by preposition "à" or another preposition (eccept "de"): - J'habite à Paris, j'y vis depuis deux ans. - J'habite en France, j'y vis depuis trois ans. - Je passe par la route principal, j'y passe tous les jours. - Je suis sur la place principale, j'y suis depuis une demi-heure. etc.