Voici, voilà, c'est : présenter quelqu'un

Ma meilleure amie, c'est elle means “This is my best friend” (literally, “My best friend, this is her”). We use c'est with a stressed pronoun PRONOMS TONIQUES to introduce a person (in this case, elle - “her”). Example: ma mère, c'est elle, et mon père, c'est lui (this is my mum and this is my dad).

We could say voici ma meilleure amie (this is my best friend), but we needed to use c'est here with the pronoun elle (her).

We could say elle est ma meilleure amie (she is my best friend), but we needed to use c'est here with the pronoun elle (her).

Mesdames et messieurs, voici la Présidente ! (Ladies and gentlemen, this is the president!). We use voici (this is/these are, here is/are) to introduce someone. Example: Voici Pierre, mon mari (this is Pierre, my husband).

We could say voici ma voiture (here's my car), but we can't use the word voiture (car) to introduce the president!

Tu vois (you see) voir, présent is not the correct phrase here. Example: tu vois souvent ta copine ? (do you see your girlfriend often?).

Ce monsieur, c'est mon père (This gentleman is my father, literally “this gentleman, this is my father”). If we have already mentioned the person we are introducing, in this case ce monsieur (this gentleman), we then use c'est to specify who they are, in this case mon père (my father). Example: cette dame, c'est la boulangère (this lady is the baker).

We could say voici mon père (this is my father), but we can't use voici (this is, here is) after ce monsieur (this gentleman).

We use il est (he is) être, présent to describe someone, not to introduce them. Example: ce monsieur, il est vieux (this man is old, literally “this man, he is old”). Age is just a number!

- Qui paye ? - C'est vous ! (-Who's paying? -You are!, literally “It's you!”). We use c'est to designate a person, in this case using the stressed pronoun vous (you) PRONOMS TONIQUES. Example: - C'est vous le chef ? - Non, c'est lui (-Are you the boss? -No, he is).

We use ce sont (these are, they are) with the pronoun eux (they), not with vous (you). Example:  - Ce sont tes amis ? - Oui, ce sont eux (-Are these your friends? -Yes, that's them).

We use voilà to mean “here is/are” or “there is/are” with a noun, not in front of a pronoun like vous (you). Example: voilà votre café ! (here's your coffee!).

- Allô, qui est-ce ? - C'est moi (-Hello, who's this? -It's me). We use c'est before the stressed pronoun moi PRONOMS TONIQUES (me). Example: - Qui est là ? - C'est moi (-Who's there? -It's me).

We use voilà to mean “here is/are” or “there is/are” with a noun, not in front of a pronoun like moi (me). Example: voilà votre taxi, madame ! (here's your taxi, madam!).

We use voici (this is/these are, here is/are) with a noun, not with a pronoun like moi (me). Example: voici ma cousine Emma (this is my cousin Emma).

Voici les champions du monde ! (here are the world champions!). We use voici (here is/are, this is/these are) in front of a noun when introducing someone, in this case les champions du monde. Example: voici mes enfants ! (these are my children!)

Ceci means “this”, so we can't use it here. Example: ceci est ma nouvelle voiture ! (this is my new car!).

We use ça va? to ask if someone is okay. If they are ok, the response is often ça va ! (I'm fine!). We can't use it here to introduce someone.

Lui, c'est Roger (this is Roger, literally “him, this is Roger”). When we use the stressed pronoun lui PRONOMS TONIQUES (him), we then use c'est (this is) to specify the person's first name (in this case Roger). Example: lui, c'est Félix, mon chat (this is Félix, my cat).

We use il est (he is) être, présent to describe someone, not to introduce them. Example: il est gentil, Roger (he's a nice guy, Roger).

We could say voici Roger (this is Roger), but we have to use c'est with the stressed pronoun lui (him).

Voilà votre dessert, monsieur (here is your dessert, sir). In this context, we use voilà before a noun to introduce or present something. Example: voilà votre thé, mademoiselle (here's your tea, miss).

We could say c'est votre dessert (this is your dessert), but in the context of a waiter serving a dish, we need to use voilà (here is). Example: c'est votre dessert ? Il a l'air délicieux ! (is that your dessert? It looks delicious!).

We use il est (it is) être, présent to describe something, not to present something. Example: il est bon, ce croissant ! (this croissant is good!, literally “it's good, this croissant!”).

 - Qui a gagné ? - Ce sont eux (-Who won? -It was them). We use ce sont (they are) with the stressed pronoun eux PRONOMS TONIQUES (them) when referring to more than one person. Example: - Ce sont tes voisins ? - Oui, ce sont eux (-Are they your neighbors? -Yes, that's them).

We use ils sont (they are) être, présent to describe people, not to introduce them. Example: ils sont très forts (they're very strong).

We use voici (this is, these are) before a noun, not before the stressed pronoun eux (they). Example: voici mes parents, Hélène et Jacques (these are my parents, Hélène and Jacques).