Voilà is one of my favorite expressions in French. It just seems so French and much more appealing than its English equivalents: ‘there is’ and ‘there are’. However, you must be careful because Il y a has the same English translation so to speak, but the meaning or useage is different. Voilà is used as if you are pointing to the object(s) you are talking about, whereas Il y a simply states the existence of the object(s) you are talking about. One practical example that you can use in an email is: Voilà, ci-joint la liste. (You can replace the underlined part with anything you are attaching). Here are some other examples to show the difference between the two expressions.
Il y a beaucoup de couples ici. (There are a lot of couples here.)
Regardez, voilà, Madame et Monsieur Dupont. (Look, there’s Mrs. and Mr. Dupont.)
Il y a un magasin de chaussures par ici. (There’s a shoe store nearby.)
Est-ce qu’il y a des grandes chaussures ? (Are there large-size shoes?)
Voilà, la pointure que vous cherchez. (There’s the size you’re looking for.)
Il y a des marchés en France. (There are markets in France.)
Voilà, le marché aux pouces de la Port de Vanves. (There’s the Port de Vanves flea market.)
