When do you use "est-ce qu'" and "est-ce que?

Exemple :
Est-ce que Marc arrive?
Est-ce qu'il arrive?

Est-ce que Marie vient avec nous?
Est-ce qu'elle vient avec nous?

The apostrophe  = ' is used to take the place of a vowel (a,e,i) when the following word begins by a vowel or a silent  h.

The animal = le animal = wrong/ l'animal = right

Est-ce que Peter vient ? = correct .= after "que" comes  "Pierre" with a consonant at the begining

Est-ce que il vient = wrong = 2 vowels so > Est-ce qu'il vient ?
you have replaced the "e" of "que" by the sign ' because two vowels followed each other.

Hope you'll understand better

have a nice day !!!

Omg it is so much but i think it will be b