y expressing place
Y replaces a preposition indicating location plus its object: 'à UIC,’ ‘à Chicago,’ ‘chez moi,’ 'devant la Tour UH' (in front of the UH Tower). It is usually translated as there. Prepositions which indicate location include à, en, dans, devant, derrière, sous, sur. The noun objects of these prepositions are places and things which indicate a place. The exception is the preposition chez which is used with a person, as in 'chez Marie' (Marie's place).
NOTE: à + person is replaced by an indirect object pronoun (lui, leur)except with certain verbs.
When these verbs are followed by a person, the disjunctive pronoun will be used, for example, “Je pense souvent à mon ami. Je pense souvent à lui.” (I often think of my friend. I often think about him.)
Placement of y is the same as that of direct and indirect pronoun objects: y comes before the verb it refers to, except in the affirmative imperative.
In compound tenses, like the futur proche and passé composé, it comes before the auxiliary.
NOTE: There is no agreement between y and the past participle.