Here's a breakdown:
* "There is/there are":
* *Il y a un chat dans la rue.* (There is a cat in the street.)
* *Il y a des livres sur la table.* (There are books on the table.)
* "Ago":
* *Il y a trois jours, j'ai vu un film.* (Three days ago, I saw a movie.)
* *Il y a dix ans, j'habitais à Paris.* (Ten years ago, I lived in Paris.)
Note: The meaning of "il y a" depends on the context.